Yearly food habits of the river otter in the Thompson Lakes region, northwestern Montana, as indicated
by scat analyses
by Kenneth R Greer
A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree
of Master of Science in Fish and Wildlife Management
Montana State University
© Copyright by Kenneth R Greer (1953)
Abstract:
A food habits study by scat analysis was conducted from April, 1952, through May, 1953, in the
Thompson lakes region of Lincoln County, Montana to help evaluate the economic status of the river
otter (Lutra canadensis) Ninety-six otter latrines supplied 1374 scats with a known date of deposit.
Material was gathered from two separate areas and analyzed data were compared. Limited sampling
was conducted to obtain a suggestion of fish abundance and "sign" was used to estimate fur bearer
numbers to help evaluate the food habits. For the entire year and for both areas fish remains were
identified most frequently, appearing in 1280 (93.2%) of the 1374 scats. Invertebrates were recorded
for 566 (41.2%), amphibians 233 (18.4%), mammals 212 (15.4%), birds 71 (5.2%) and reptiles 5
(0.4%). Each of these groups retained the same position in relative importance throughout all seasons
except fall when mammals replaced amphibians for third.
The data suggest availability of prey to be important in determining the food habits’ of the otter. /
I:
© M T A i m S T A T E O M B W E i^ S S T Y
IEAELT FOOD HABITS OF THE..EIVER OTTER1IN THE THOMPSON LAKES REGION,
NORTHWESTERN MONTANA, AS INDICATED BY SCAT ANALYSES '
;
5j
KEMETH R. GREER
I
A THESIS
I
S u b m itted t o th e G rad u ate F a c u lty
fti
in
I:
'
by
p a r t i a l f u l f i l l m e n t o f th e re q u ire m e n ts
f o r th e degree o f
M aster o f S cien ce i n F is h , and W ild lif e .Management
at
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M ontana S ta te C o lleg e
Approved!
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XHe dd,
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i
d e p a r tm e n t
C hairm an, Exam ining Committee ^
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a n , G fadhate D iv is io n
II
Bozeman, Montana
A ugust, 1953
108559
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2-
I
TABLE OF CONTENTS
II
Page
A b s tra c t ......................................................................
3
I n tr o d u c tio n ..............................................................
U
The s tu d y a r e a .................... .....................................
U
Methods .........................................................................
8
R e s u lts .........................................................................
lit
Comparison o f Thompson and Gary a re a s
18
Tapeworm in c id e n c e ......................................
23
D is c u s sio n ..................................................................
23
C o n clu sio n s and recom m endations ....................
26
Sum m ary.................. ......................................................
27
L i t e r a t u r e c i t e d .......................................... ..
29
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ABSTRACT
A food h a b i t s s tu d y b y s c a t a n a ly s is was co nducted from A p r il, 1952,
th ro u g h May, 1953, i n th e Thompson la k e s re g io n o f L in c o ln C ounty, Montana
to h e lp e v a lu a te th e economic s t a t u s o f th e r i v e r o t t e r (L u tra c a n a d e n s is )
H in e ty - s ix o t t e r l a t r i n e s s u p p lie d 137k s c a ts w ith a known d a te o f de­
p o s i t . M a te r ia l was g a th e re d from two s e p a ra te a re a s and a n a ly z e d d a ta
were com pared. L im ite d sam pling was co nducted to o b ta in a s u g g e s tio n o f
f i s h abundance and " sig n " was u s e d t o e s tim a te f u r b e a r e r numbers to h e lp
e v a lu a te th e food h a b i t s . For th e e n t i r e y e a r and f o r b o th a re a s f i s h
rem ain s were i d e n t i f i e d m ost f r e q u e n tly , a p p e a rin g i n 1280 ( 93. 2%) o f th e
137k s c a t s . I n v e r te b r a te s were re c o rd e d f o r 566 ( L i . 2^ ) , am phibians 253
(ldok% ), mammals 212 ( 1 5 .1 $ ) , b ir d s 71 i5»2%) and r e p t i l e s 5 (0»1$)* Each
o f th e s e groups r e ta in e d th e same p o s i t i o n i n r e l a t i v e im p o rtan ce th ro u g h ­
o u t a l l seaso n s e x c e p t f a l l when mammals re p la c e d am phibians f o r t h i r d .
The d a ta s u g g e s t a v a i l a b i l i t y o f p re y to be im p o rta n t i n d e te rm in in g th e
fo o d h a b its ’ o f th e o t t e r .
I-
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O
$,
INTRODUCTIOM
I
O tte r s (L u tra c a n a d e n s is ) have been p r o te c te d i n Montana s in c e th e
Si:'
‘i
19U9-50 tra p p in g se a so n b u t th e r e i s ev id en ce t h a t a few a re u n in te n tio n ­
i'
a l l y ta k e n i n tr a p s and th e r e a re rum ors t h a t some a re e lim in a te d b y a c ts
•t
i'
o f v a n d a lism .
C e r ta in unfounded r e p o r ts from L in c o ln C ounty in d ic a te d
th e s e anim als a re u n d e s ir a b le .
Some fish e rm e n c la im th e y red u ce th e
numbers o f t r o u t and b a s s and th u s c o n tr ib u te to p o o r f i s h i n g .
tr a p p e r s d e c la re o t t e r s d e s tr o y m u s k ra ts, b e a v e rs and m inks.
Some
A su rv ey
o f .t h e l i t e r a t u r e d id n o t r e v e a l in fo rm a tio n to s u b s ta n tia te o r r e f u te
l'
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th e s e c laim s so i t seemed d e s ir a b le to co n d u ct a s tu d y .
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The w r i t e r w ish es to th a n k th e Montana F is h and Game D epartm ent f o r
f i n a n c i a l su p p o rt and a ls o F le tc h e r E . Mewby o f t h i s d ep artm en t f o r h is
i n t e r e s t and c o o p e ra tio n d u rin g th e p r o j e c t .
S in c e re a p p r e c ia tio n i s
-e x te n d e d t o D r. Don C. Quimby f o r encouragem ent and guidance d u rin g th e
s tu d y and c r i t i c a l re v ie w o f th e m a n u sc rip t.
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THE STUDY AREA
k
7
'
The i n v e s t i g a t i o n was c e n te re d around Thompson L ak es, a group o f 31
la k e s and s tre a m s , s i t u a t e d a p p ro x im a te ly 1|0 m ile s s o u th e a s t o f L ib b y ,
F '
I " ';"
M ontana (F ig . l ) .
These la k e s a re e a s i l y a c c e s s ib le and many can be seen
from U. S'. Highway Mo. 2 .
F is h e s n a tiv e to th e a re a in c lu d e : Kokanee salm on ( O nchorhynchus.
n e r k a ) , d o l l y v ard en t r o u t ( S a lv e li n u s malma) , c u tth r o a t t r o u t (SaImo
I
I
I
*
' c l a r k i i ) , ro c k y m ountain w h ite f is h ( Prosopium w illja m s o n i) , Columbia
r .•
S
}:
c o a rs e s c a le d s u c k e r (C atostom us m a c ro c h e ilu s ), Columbia lo n g -n o se d
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B
A
I
S
I
Yx
I
*
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>:
-Gi
s u c k e r (C atostom us c a to sto m u s) , r e d - s id e d s h in e r (R ic h a rd s o n iu s h a l t e a t u s ) ,
s c u lp in (C o tta s p a n c t a l a t a s ) , sq u aw fish ( P ty c h o c h e ilu s o re g o n e n s is ) and
Columbia r i v e r chub (M ylocheilu s c a u r in u s ) .
two w ere common.
H ybrids betw een th e l a t t e r
E x o tic s in c lu d e : E a s te r n brook t r o u t (S alv e l i n u s fo n »<
t i n a l i s ) rainbow t r o u t ( Salmo g a i r d n e r i i ) , larg em o u th b a ss (M icro p teru s
}
s a lm o id e s) , y e llo w p e rc h ( P e re a f la v e s c e n s ) and pumplcinseed (Eupomotis
g ib b o s u s ) .
A ccording to Echo (p e rs o n a l com m unication) th e r e e x i s t s an
o v e r p o p u la tio n o f p e rc h and s u n f is h .
G i l l n e t s , e l e c t r i c sh o ck in g equipm ent and f is h in g were employed to
o b ta in in fo rm a tio n on f i s h abundance i n th e v a rio u s w a te rs (T ab le I ) .
i
An
i n d i c a t i o n o f m u sk rat ( O n d atra) , mink (M u ste la ) , and b e a v e r (C a s to r) num­
b e rs was a ffo rd e d by " sig n " (T able I I ) .
G a ry 's L ake, ab o u t 20 m ile s due n o rth o f th e Thompson Lake a re a was
in c lu d e d f o r com parison because i t i s somewhat i s o l a t e d and s u p p o rts a
g r e a t e r c o n c e n tr a tio n ' o f f u r b e a r e r s .
Only on th r e e o c c a sio n s were p a i r s o f o t t e r o b serv ed w ith in th e stu d y
a re a s.
Few s i g h t re c o rd s w ere r e p o r te d .
L ie r s (l9 J ? l), o b serv ed dens o f
th r e e l i t t e r s a lo n g a 20 m ile s t r e t c h o f stre a m i n M in n eso ta.
were se e n i n t h i s s tu d y .
f o r 2 h o u rs .
No dens
Two o t t e r were o b serv ed on a s m a ll la k e (8 a c r e s )
They were n o t o b serv ed to e a t a n y th in g .
D uring th e $-10
m in u te s th e y were on th e s h o re th e y d e p o s ite d 3 d ro p p in g s,
T h is one
d i r e c t o b s e rv a tio n was n o t s u f f i c i e n t to d eterm in e th e number o f s c a ts
d e p o s ite d by an o t t e r i n a g iv en le n g th o f tim e .
I''
The number o f s c a ts
c o l l e c t e d a t l a t r i n e s betw een known d a te s , and known o r e s tim a te d d a te s
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-7 Table I .
R e la tiv e abundance■o f f i s h i n s tu d y a re a as in d ic a te d
by li m i t e d sam p lin g .
A rea and Date
Thompson
(9 sam pling a r e a s ,
see f i g . I )
J u n e -A u g ..
S e p t. 3
a
J u n e -S e p t.
May, Aug.
S',’.-'
S'.v
G a ry 's
( l - a re a )
Sam pling Method
Catch
7 h r. fis h in g
(h a re a s )
50 IP i n 2 h r s . , 100 SF i n 3
h r s . , 10 SU i n I h r . , 12 CRC,
8 SF i n I h r .
76 SC, 21 SU, 16 T, 10 S ,
7 W , 3 SH
e l e c t r i c ' shocking
( 2-100 f t . stream
s e c tio n s )
*70-2lt h r . g i l l
n e t s e t s ( I a re a )
13- 2lt h r . s e t s
(3 a re a s )
(a v . c a tc h p e r 2k h r . s e t )
63 I P , 35 MF3 17 S 3 7 S F 3 I SU
28 SF, 22 S , Ih CRC, 6 B, 3 T,
2 W 3 I SU
2 h r s . f is h in g
it SH9 2 T
E -b a s s , CRC-Columbia r i v e r chub, 5 -s u c k e r, S C -s c u lp in , S F -sq u aw fish ,
SH- s h i n e r , S U -su n fish , T - t r o u t , W - w h ite f is h , IP -y e llo w p e rc h .
p '
Ir
w
KThe d a ta o f 70 g i l l n e t s e t s were s u p p lie d b y John Echo w h ile w orking
on a f i s h s tu d y i n th e low er Thompson Lake.
P
i
Table U e ' R e la tiv e abundance o f f u r b e a r e r s i n s tu d y a r e a as
in d ic a te d by " s i g n " .
A rea
Thompson
- ( 9 sam pling a r e a s )
G a ry 's " ..
( I . a re a )
Av. n o .
b e av e r
houses
AV.
b e av e r
"sig n "
Av.
m uskrat
"sig n "
Av.
mink
" sig n "
1 .3
%
XX
X
3 .0
XXX
XXX
X
I ;'.v
X -L ig h t, XX-M oderate, XXX-Heavy
U.'
v r>
-i. \
of. s c a t d e p o s itio n , re v e a le d few o t t e r i n th e a r e a .
rem ained o n ly a day o r two i n any one l o c a l i t y .
Those p r e s e n t u s u a ll y
A ccording to L ie r s (op
C i t ) , " I n d iv id u a ls may co v er 5>0 to 60 m ile s o f stre am c o u rse i n a y e a r .
F a m ilie s ran g e about 3 to 10 m ile s i n a c u r r e n t s e a s o n " .
The e x te n s iv e
home ran g e o f th e o t t e r i n th e s tu d y a re a i s in d ic a te d by th e d a te s s c a ts
w ere d e p o s ite d a t known l a t r i n e s .
D uring s p r in g , th e d e p o s its seemed to
show a v i s i t to an a re a f o r a day o r tw o, a b s e n t 2 o r 3 d a y s, r e t u r n f o r
a day and a b s e n t 2 o r 3 d a y s.
T his p a t t e r n was re p e a te d 3 o r U tim es
th e n an absence betw een v i s i t s o f 7 to l £ days o c c u rre d .
o f v i s i t s d e c re a se d as summer p ro g re s s e d .
The fre q u e n c y
S c a t ev id en ce s u g g e s te d t h a t
o t t e r s d e s e r te d th e la k e s when th e y became fro z e n o v e r.
The f a c t t h a t ■
d ro p p in g s were d e p o s ite d on th e same day a t G ary’ s and th e Thompson a r e a ,
s e p a r a te d by 28 w a te r m ile s , in d ic a te d each o f th e s e a re a s s e rv e d as
s e p a r a te home ra n g e s f o r th e o t t e r i n h a b i t a n t s .
The number o f o t t e r s
e s tim a te d t o u se th e s tu d y a re a was 6- 8 .
METHODS
" P u llin g o u t" p la c e s and l a t r i n e s (L i e r s , op c i t ) were lo c a te d by
w alking th e s h o r e s .
Most l a t r i n e s were on th e s h o re s , s e v e r a l w ere on o r
n ear beaver houses.
F a lle n t r e e s , l a r g e r th a n 18 in c h e s i n d ia m e te r, ex­
te n d in g from th e sh o re i n t o th e w a te r were o f te n u s e d .
L a tr in e s appeared
to be o f lo n g e s ta b lis h m e n t.
O tte r s c a ts a re r e a d i l y re c o g n iz e d w ith e x p e rie n c e .
The av erag e i s
a p p ro x im a te ly 3 /b in c h e s i n d ia m e te r and c h a r a c t e r i s t i c a l l y i n 2 , 3 , o r U
c u rv ed segm ents each a b o u t 1^-3 in c h e s lo n g making a t o t a l le n g th o f lt-7
-
in c h e s .
O
9-
I t i s n o t u n u su a l f o r d ro p p in g s to v a ry i n s iz e from above a v e r­
age t o a rem nant.
t e r i s t i c o d o r.
F re s h d ro p p in g s were u s u a l l y 'b l a c k w ith a s tr o n g c h a ra c ­
They u s u a ll y c o n s is te d o f f i s h s c a le s and bones a lth o u g h
o th e r m a te r ia ls such a s h a i r , f e a t h e r s e t c . were f r e q u e n tly p r e s e n t.
Heavy mucus was mixed th ro u g h o u t a f r e s h s c a t .
c re a s e i n mucus c o n te n t p ro g re s s e d w ith a g e .
D ry in g , c r u s tin g and de­
To d eterm ine th e r a t e o f
change, f r e s h s c a ts w ere ta g g e d , l e f t u n m o lested and r e v i s i t e d d a ily .
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D roppings from immature o t t e r c o u ld be m ista k e n f o r th o se from a la r g e
mink i f i t were n o t f o r th e s m a lle r d ia m e te r o f th e l a t t e r and th e c h a ra c ­
t e r i s t i c one segment (F ig . 2 ) .
An o c c a s io n a l " sig n " n o tic e d a t a l a t r i n e s i t e was a w h ite d isc h a rg e d
s u b s ta n c e .
c h a rg e .
Some tr a p p e r s r e p o r te d t h i s to be "phlegm" from an o r a l d i s ­
I t was u s u a l l y found s e p a ra te from th e s c a t s b u t i n t h e i r v i c i n i t y .
I t h ad an i r r e g u l a r form ( l / 8 t o 1 /h in c h t h i c k and I t o 2 in c h e s lo n g ),
'O
w h ite opaque c o lo r , e l a s t i c q u a l i t y and a p p a r e n tly was la c k in g i n o d o r.
y e llo w tin g e accom panied a g in g .
A
One tr a p p e r was r e p o r te d to have u se d t h i s
m a t e r i a l t o make s c e n t f o r tra p p in g o t t e r .
' TflIhen a l a t r i n e was d is c o v e re d a l l s c a ts were aged and p la c e d i n se p a r a t e e n v elo p e s on w hich e s s e n t i a l d a ta were re c o rd e d .
'
Once th e lo c a t io n
o f a l a t r i n e was e s ta b lis h e d i t was v i s i t e d r e g u l a r l y f o r s c a t c o l l e c t i o n s .
E ig h t w ere lo c a te d a t G ary’s Lake and 88 on th e Thompson s tu d y a r e a .
Snow
made a c c e s s i b i l i t y t o th e a re a s d i f f i c u l t th ro u g h o u t th e w in te r and f a l l
b u t 6 c o l l e c t i o n s were made.
F in a l c o l l e c t i o n s were made a f t e r a l l snow
d is a p p e a re d and " l o s t " drop p in g s were re c o v e re d .
was c o l l e c t e d from A p r il, 1 9 # , th ro u g h May, 1 9 # .
-Y
A t o t a l o f 2209 s c a ts
The approxim ate d a te o f
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f M ’ T O lf* V * ............--------------------- ................... , r
F ig . 2 .
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O tte r s c a t above, mink below .
-
I
11 -
d e p o s itio n was d eterm in ed f o r 137b w hich c o n s t i t u t e th e b a s is o f t h i s
:'0
Iv 5
s tu d y .
A n a ly sis o f d ro p p in g s was accom plished i n th e d ry s t a t e „
S c a ts were
b ro k en a p a r t i n a c u ltu r e d is h w ith d is s e c tin g n e e d le and tw e ez e r and ex­
f>V-’
amined under a 2Ox b in o c u la r m ic ro sco p e „
S m a lle r ite m s , such a s h a i r s
and p a r t s o f f e a t h e r s , were reexam ined u n d er th e compound m ic ro sco p e .
!?
The
com plete s c a t was s e a rc h e d f o r re c o g n iz a b le rem ain s o f item s i n th e d i e t .
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I
These w ere i d e n t i f i e d by com parison w ith re f e r e n c e c o l l e c t i o n s o f b o n es,
h a i r , f e a t h e r s , and o th e r u n d ig e s tib le m a te r ia ls o f v e r te b r a te s and i n ­
I
v e rte b ra te s ,
I d e n t i f i e d ite m s w ere re c o rd e d on th e c o l l e c t i n g e n v e lo p e ,
p la c e d i n a s m a lle r envelope and r e tu r n e d t o th e c o l l e c t i n g en v elo p e along
w ith u n i d e n t i f i a b l e re m a in s .
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AU re c o rd s w ere l a t e r t r a n s f e r r e d t o a £ by
V:
8 in c h punch c a rd w hich p ro v e d in v a lu a b le i n c u m u latin g and s o r tin g d a ta
( F ig . 3) o These d a ta w ere ta b u l a t e 4 i n m onthly p e rio d s th e n grouped in to
s e a so n s as fo llo w s :
W in te r- J a n u a ry , F e b ru a ry , March; S p rin g - A p r il, May,
Ju n e; Summer- J u ly , A ugust, Septem ber; and F a l l - O cto b er, November, Dec­
SI
3
V
:
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V
em ber. The d a ta were e v a lu a te d by th e o c cu rren c e o f s p e c ie s o n ly ( S c o tt 1 9 b l,
Orabb 1 9 k l , F e r r e l , e t a l , 1933)*
i ;
p
I
F or exam ple, i f rem ains o f s i x s u n fis h
a p p e a re d i n a s c a t th e y were re c o rd e d as one o c c u rre n c e .
The p e rc e n t
o c c u rre n c e was c a lc u la te d by d iv id in g th e number o f s c a ts o f a p e r io d i n t o
th e number o f o c c u rre n c e s o f s p e c ie s f o r th e same p e rio d .
R eferen c e c o l l e c t i o n s were p re p a re d as fo llo w s :
P re lim in a ry s c a t
e x am in atio n s re v e a le d many i d e n t i f i a b l e o b j e c t s , e s p e c i a l l y bones and
i
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12 -
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m m m k i
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V arious S k e le ta l E lem ents
Top row:
Bass
T ro u t
Frog
2nd. row :
Bass
Sucker
W h ite fish
P h ary n g eal T eeth
3 r d . row : Columbia R iv er Chub, Squaw fis h , Squaw fish
O to lith s
P e rc h , W h ite fish
S c u lp in , Bass
V
arious
S
k
e
le
ta
l
E
lem ents
P h a ry n g e a l T eeth
Toad,
F
ro
g
,
S
q
u
aw
fish
,
Columbia
L iv e r Chub
L t h . row:
Bass
Bass
P
e
rc
h
,
P
e
rc
h
,
S
quaw
fish,
Columbia
R iv e r Chub
S u n fish Perch
5 t h . row :
Bottom row : Punch c a r d . F e a th e r c a rd s
F ig . 3 .
R e p re s e n ta tio n o f re fe re n c e c o lle c tio n s u sed to i d e n t i f y
d ia g n o s tic ite m s found i n s c a t s .
-1 3 s c a le s o f f i s h e s .
O ther o b je c ts in c lu d e d bones o f v a rio u s v e r t e b r a t e s ,
h a i r , f e a t h e r s , t e e t h , claws, and e x o s k e le ta l p a r t s o f i n v e r t e b r a t e s .
V e r te b r a te s and in v e r te b r a te s found i n and around o t t e r h a b i t a t were
c o lle c te d .
■
F re sh specim ens o f f i s h e s , fro g s (Rana p r e t i o s a ) , to a d s (Bufo
'\
b o r e a s ) , sn ak es ( Thamnophis e le g a n s ) , salam anders ( Ambystoma m acrod acty lu m ) , and l i z a r d s (G errh o n o tu s c o e r u le u s ) , were red u ced to s k e l e t a l
re m a in s b y b o i l i n g i n w a te r 3 -5 m in u te s .
C h a r a c t e r i s t i c bones o f each
s p e c ie s such as s c a l e s , p h a ry n g e a l t e e t h , o t o l i t h s , m a x illa ry , o p e rc u la r ,
p r e o p e r c u la r , d e n ta r y , v e r te b r a and o th e rs were s e p a ra te d and mounted on
c o lo re d c a rd s (F ig . 3 ) .
A few mammals were lik e w is e p re p a re d b u t th e
a v a i l a b i l i t y o f th e c o l l e c t i o n a t Montana S ta te C o lleg e made i t u n n eces­
s a r y to p re p a re com plete c o l l e c t i o n s .
R eferen c e h a i r c o ll e c t i o n s were r e s t r i c t e d t o f u r b e a r e rs ( o t t e r ,
b e a v e r, m u sk ra t, m in k ).
Only th e s e anim als were c o n sid e re d i n th e s tu d y .
R eferen c e s l i d e s were made o f th e f u r and g u ard h a i r s from th e n e c k ,
c h e s t, b a c k , rump, abdomen, s id e and t a i l .
S c a la t io n , m ed u lla s t r u c t u r e
and m easurem ents were u sed as a b a s is f o r com parison w ith unknowns found
i n th e s c a ts (M athiak 1938, Mayer 1 9 5 2 ).
A few b r e a s t f e a th e r s from r e p r e s e n ta tiv e s o f th e b i r d o rd e rs found
i n and around th e w a te rs were mounted on c a r d s .
F e a th e rs i n s c a t s were
compared b u t o n ly th o s e o f th e A natidae and g re b e s were i d e n t i f i e d .
S h a ft
form s (ro u n d , f l a t , o v a l) , b arb e c o n c e n tra tio n a t th e b ase w ith p o in t o f
d e p a r tu re from s h a f t and b a rb u le b a se s were c h a r a c te r s u se d f o r s e g r e ­
g a tio n s .
A ll s c a t s and r e f e r e n c e c o lle c tio n s u se d i n th e s tu d y a r e a t
Montana S ta te C o lle g e .
O
I:
i: i
-U i' RESULTS
O
The r e s u l t s o f th e s c a t a n a ly s is a re e x p re sse d i n Table IX I b y re c o rd ­
in g th e number and p e r c e n t o f th e s c a ts i n which an ite m ( s p e c ie s ) was
r e p r e s e n te d .
A s c a t u s u a ll y c o n ta in e d more th a n one o f th e ite m s r e p o rte d
i n th e ta b le and th e r e f o r e none o f th e p e rc e n ta g e s t o t a l 100$.
F o r th e e n t i r e y e a r and f o r b o th a re a s f i s h rem ains were i d e n t i f i e d
m ost f r e q u e n tly , a p p e a rin g i n 1280 (9 3 .2 $ ) o f th e 137i| s c a t s .
.
i
I h v e r te -
b r a te s w ere re c o rd e d f o r # 6 ( L i . 2 $ ), am phibians 2 # ( l8 .L $ ) , mammals 212
-
( I S M 9 b ir d s 71 (5*2$) and r e p t i l e s 5 (O .L $).
Each o f th e s e groups r e ­
ta in e d th e same p o s itio n i n r e l a t i v e im p o rtan ce th ro u g h o u t a l l sea so n s
e x c e p t f a l l when mammals r e p la c e d am phibians i n t h i r d p la c e .
L a g le r and
O s te n s o n 's ( W ) summery o f e a r l y s p r in g fo o d o f o t t e r s i n M ichigan, W
and ISUL9 showed stom ach ( i n p e r c e n t o f t o t a l volume o f food) and i n t e s t i ­
O
n a l a n a ly s is ( in av erag e e s tim a te d p e r c e n t o f fo o d by b u lk ) to b e :
Game
and pan f i s h e s (3 2 .0 $ and 1 5 .9 $ ) , fo ra g e f is h e s (1 7 .6 , 2 2 .7 ) , f i s h rem ains
( 3 .0 , 1 3 .8 ) , f r o g s and mudpuppies (1 6 .1 , 7 . 5 ) , o th e r v e r te b r a te s (2 5 .8 ,
0 . 9 ) , i n s e c t s ( 0 .8 , L .2 ) , and c r a y f is h (!4. 7 , 3 5 .0 ) r e s p e c t i v e l y .
Of th e f i s h , s u n f is h o c c u rre d m ost f r e q u e n tly , 5 8 .2 $ o f a l l s c a t s .
I t was m ost f r e q u e n t i n summer s c a t s ; 72. 8$ o f th e 60I4 a ss ig n e d t o t h a t
season.
I t was th e m ost commonly re p r e s e n te d f i s h d u rin g a l l se a so n s
e x c e p t w in te r when i t was s u rp a s s e d b y th e s u c k e r.
(3 3.3% ).
S uckers ra n k e d second
They were m ost p ro m in en t i n w in te r (5 9 .6 $ ) and f a l l ( li5 .3 $ ) .
The f i s h t h i r d i n im portance was th e s c u lp in which o c c u rre d i n 21$ o f a l l
s c a t s and was u n ifo rm ly r e p r e s e n te d th ro u g h o u t th e f o u r s e a s o n s .
O
A ll o f
i!
j i;
“’ll?"
O
XiLiXHjaj-L^UNU
Frog ■
✓
V 7 e-Ly -LXf
K-Ly
ovy xxu \X 7oy/
67
250
7
5
5
71
29
' 32
10
16
22
782
239
52
69
60
( 7 .9 )
( 5 .6 )
( 58 . 2 ) .
(3 3 .3
( 3 .8 )
( 5 .0 )
8
9
59
Hi
( 5.5)
( 8.1)
( 1 8 .2 ) < ’
( O o5L
Salam ander
( oTTT)
REPTILES
( 'o .lT
Snake
( 5 .2 )
BIRDS
( 2 . 1) .
Unknown
( 2 .3 )
Duck
(
0 .7 )
Grebe
MAMMALS
gig a s , ui
^ T T tT T
Unknown
130 ( 9.5)
O tte r ( t r a c e )
10 ( 0 . 7 )
Beaver
61 ( l .l )
M uskrat
W
oom
m
m
i
o
«
O
B
o
o
o
»
2 ( 0 .1 ) ’
2 ( 0.3)
Meadow mouse
I
( 0.1)
I ( 0 .2 )
Shrew
mmmwmmmmm
2 ( O .l)
I ( 0 .2 ) - — —
Mink
I ( 0 .2 )
I f 0.1)
I ( 0 .2 )
Ground s q u i r r e l
* F i r s t f ig u r e i s th e number o f s c a ts th e ite m ap p eared w ith in , The
fig u r e i n b ra c k e ts i s th e % of. s c a ts th e ite m ap p eared w ith in «
** U ndeterm ined e x o s k e le ta l frag m en ts o f a q u a tic i n s e c t s .
I
29
32
10 ____ L
311
197
9
10
j
!
i
5l
13
I
2
I
I
^
0
CQ
20
0
I
n
g
£>
& '
S 1 •P
U
h
P
i>
" ©
50)
SH-
133
I
h
38
6
6
16
327
• 1
102
....
-■
112
I
2
130
10
61
2
1
2
1
82
61
82
B a s i-h y a l
(Tongue)
17
12
I 103
H
11
233
125
217
P a la tin e
16
157
(21. 0) :
/ xxc-ovy
• 9 ( 9.1} 117 (1 9 .6 ) 116 (1 9 .2 ) 8 (1 0 .7 )
oaOSQOWDB(M
lUimM 2 ( 0*3)
I ( 0 .7 ) I ( 1 .3 )
«*JUlM
OMUOHOUUOoCO I ( 0 .2 )
I4. C OeY)
WWWOOW
^ Oo Y) wwwooeooammm
I ( 0 .2 )
5 ( 5 .1 ) 10 ( 6 .7 ) 12'5 ( 1 .1 ) 1 ( 1 .3 )
^ lo3) wmwmmwaamm
I ( 1 .0 ) 19 ( 3 .2 )
I
l
( 2 .3 ) I ( 1 .3 )
I ( 1 .0 ) 13 ( 2 .2 )
2
^
0e2) wcuwmeuwwww
8 ( 1 .3 )
88
(1
1
.8
)
101
(1
7 .2 ) 12 (1 6 .0 )
8 ( 8 .I T
3
(
0
.5 ) — ——
I ( 1 .0 )
3 ( 0 .5 )
72
(1
1
.9 ) 10 (1 3 .3 )
6 ( 6 .1 ) 12 ( 7.0)
I
(
0
.2
) I ( 1 .3 )
I ( 1 .0 )
7 ( 1 .2 )
«oaanweaComOBeam 33 ( 5.5) 27 ( 1.5) I ( 1.3)
175
i5 o
91
25
526
291
92
180
13
11
276
113
17!
I
H ypural
(ii.o )
( 0 .7 )
(9 3 .2 J
( i B.5)
I n te r o p e r c u la r
( 8. 2)
P re o p e rc u la r
m rjr
( 0 .9 )
( 10, 0)
( 3 .6 )
( 1 .3 )
O to lith
INVERTEBRATES'
*26 ( 26. 3 ) 2W CU1 . 6 ) 267 (UU.2 ) 2$ (3 3 .3 )
•^A q u atic I n s e c ts
5 T J T l J 117 (1 9 .6 ) 116 (19. 2 ) 8 (1 0 * 7 )' 211
12
6 ( 1. 0) I ( 1 .3 )
W ater "Bug""
3 ( 3 .0 )
2 ( 0. 3)
A quatic B e e tle
5 ( 5 .1 ) 71 (1 1 .5
52 ( 8 . 6) 9 (1 2 ; o ) 137
50
Stone Fly" Nymphs
6 ( 6*1) 27 ( U.5
Iii ( 2 .3 ) 3 ( 1 .0 )
18
Dragon F ly
—
8 ( 1 .3 ) 10 ( 1 .7 )
Dragon F ly Nymphs
8
8 , 1) k7 ( 7 .9 ) 52 ( 8.6) 5 ( 6 .7 ) 112
Fresh"W ater Shrimp k
L.o) 85 (lU .3 ) 51i ( 8 . 9) 8 (10*7) i5 i
6 ( 1 . 0)
M illip e d e
—9
3 ( o .5 )
FISHES
1280
99 ( 1 0 0 J 315 (9 1 .1 ) 561 (9 2 .9 )
T ro u t
29" (2 9 .3 ) 111 (2 3 .7 ) 59 ( 9 .8 )^ 2 5 X 3 3 ^ 3 7 251
289
S c u lp in '
25 (2 5 .3 ) 122 (2 0 .2 ) 126 (2 0 .9 ) 16 (2 1 .3 )
Squaw fish
6 ( 6 .1 )
18 ( 8 * l)
53 ( 8 .8 )
I ( 1 .3 ) 108
Columbia R. Chub
21 (2 1 .3 )
18 ( 8 .1 )
3 ( 0.5)
5 ( 6 .7 )
77
S u n fish
33 (3 3 .3 ) 281 ( l 7 . l ) IlO (7 2 .8 ) 15 (6 0 .0 ) 799
Sucker
59 (5 9 .6 ) 237 (3 9 .8 ) 127 (2 1 .0 ) 3 l (1 5 .3 ) 157
52
W h ite fish
10 ( l O .l )
27 ( 1 .5 )
I ( 0 .6 ) 11 ( l l . 7 )
Bass
I ( 1 .0 )
30 ( 5 .0 )
35 ( 5.8) —-----—* 69
75
P erch
7 ( 7 .1 )
36 ( 6 .0 )
28 ( 1 .6 )
I ( 5 .3 )
75' (1 2 .6 ) l l ( 2 .3 ) 13 (1 7 .3 ) l l 6
S h in e r______________ U ( H . l )
D en tary
137k
T eeth
75
I
I
C la v ic u la r
6oU
H
H a ir
TOTAL
; P h a ry n g e a l te e t h
#6
FALL
D ia g n o stic p a r t s u sed f o r i d e n t i f i c a t i o n a re shown.
Claw
No. s c a ts :
SUMMER
Foot
SPRING
S c a le
ZENTER
N o rth w estern M ontana.
M a x illa
S p e c ies i d e n t i f i e d i n 137k . o t t e r s c a ts from th e s tu d y a re a s in,
F e a th e r
O
Table H I e
j
LjJ
-
16 -
th e above f i s h e s o c c u rre d i n 20% o r more o f th e s c a ts f o r each o f th e
O
seaso n s.
T ro u t -were f o u r th i n o c cu rren c e (l8<,£$) b u t showed low r e p r e ­
s e n ta tio n i n summer (9o8%) and h ig h i n f a l l (33°3%).
s e n te d o c c u rre d i n l e s s th a n 10% o f th e d ro p p in g s .
O th er f i s h r e p r e ­
Jn o rd e r o f o c cu r­
r e n c e , th e y w ere: s h in e r , sq u a w fish , Columbia r i v e r chub, p e rc h , b a ss
and w h ite f is h (s e e Table I I I ) .
I
Many s c a ts c o n ta in e d s m a ll i n s e c t rem ains t h a t co u ld have been in
th e a lim e n ta r y c a n a ls o f f i s h ta k e n by o t t e r .
L a g le r and O stenson (l9l|.2)
con clu d ed t h i s i n t h e i r s tu d y o f o t t e r stom achs and i n t e s t i n a l t r a c t s .
i
The l a r g e r i n s e c t s r e p r e s e n te d in th e s c a ts were c o n sid e re d a s a food
ta k e n d i r e c t l y by th e o t t e r .
I n v e r te b r a te s c o n sid e re d as food w ere i n 5)66 o r ltl.2% o f th e 137h
s c a ts .
0S
The c a te g o ry " a q u a tic in s e c t s " (17.5%) ap p eared to be m o s tly f r a g ­
m ents o f dragon f l y nymphs (O donata) (T ab le U l ) .
I f t h i s assu m p tio n i s
c o r r e c t , th e n dragon f l y nymphs (8 .2 $ p lu s ll^ q u a tic in s e c ts " 17o5$)
,1
1
t
o c c u rre d m ost f r e q u e n tly i n th e group fo llo w e d b y f r e s h w a te r shrim p
(Gammarus) ( l l o0$) and a q u a tic b e e tl e s (C o le o p te ra ) (1 0 .0 $ ) .
The g r e a te s t
o c c u rre n c e o f in v e r te b r a te s ap p eared i n s p r in g (ltl.6 $ ) and summer (Ijli.2 $ ) .
The r e p r e s e n ta tio n f o r th e w in te r and f a l l was 2 6 .3 and 3 3 .3 $ r e s p e c tiv e ly .
Frog rem ains a p p ea re d i n 250 o r 1 8 .2 $ o f th e d ro p p in g s.
and summer r e p r e s e n ta tio n was 1 9 .6 and 1 9 .2 $ r e s p e c t i v e l y .
9 .1 and 1 0 .7 $ o f w in te r and f a l l s c a t s .
The s p rin g
They were i n
Salam anders were r e p r e s e n te d by
<
«y
i
a t r a c e i n a l l p e rio d s e x c e p t w in te r .
Mammal rem ains o r t r a c e s o f h a i r were found i n 212 o r l5 .U $ o f th e
!
-i •
i
S K W '
IlC
to ta l.
O
P e rio d ic d if f e r e n c e s showed th e w in te r t o be lo w e s t (8.1%) w ith
th e o th e r seaso n s ra n g in g from l i t . 8 to 17.2%.
One hundred and t h i r t y
(9o$%) d ro p p in g s c o n ta in e d a tr a c e o f o t t e r h a i r .
A tr a c e was c o n sid e re d
as such i f i t were p o s s ib le to make 3 o r more e x am in atio n s l i d e s from th e
m a te ria l.
O tte r h a i r was n e v e r found i n g r e a t e r q u a n tity th a n an l / 8 in c h
t u f t s u g g e s tin g i t was ta k e n w h ile th e o t t e r was grooming i t s e l f .
F is h e r
(l9 h 0 ) and M urie (191*0) have o b serv ed th e s e a o t t e r (Snh y d ra l u t r i s )
sp en d in g much tim e c le a n in g i t s e l f and i t s young.
M uskrat was i d e n t i f i e d in 6 l (luU%) o f th e s c a t s .
The o c cu rren c e
was c o n c e n tra te d i n s p rin g 33 (5.5%) and summer 27 (I*.5%), a b s e n t i n
w in te r and i n one s c a t f o r th e f a l l p e r io d .
B eaver was i n 10 (0.7%) w ith
g r e a t e s t o c c u rre n c e 7 (l.2% ) i n th e s p rin g and showing i n one s c a t f o r
e ac h o f th e o th e r th r e e s e a s o n s .
O
Mink, meadow mouse (M ic ro tu s ) , shrew
(S o rex ) , and ground s q u i r r e l (C i t e l l u s ) were a ls o i d e n t i f i e d .
Of th e 71 (5.2%) s c a t s c o n ta in in g f e a t h e r s , 29 were u n d e term in e d , 32
(2<>3%) had duck and 10 (0.7% ) c o n ta in e d grebe f e a t h e r s .
F e a th e rs appeared
i n 1*0 (6.7% ) s c a t s from th e s p rin g c o l l e c t i o n , 2% (1*.1%) from th e summer,
£ (5*1%) i n w in te r and I (1.3% ) i n f a l l .
The M ichigan s tu d y o f L a g le r and O stenson (l9l*2) r e v e a le d a lim it e d
o c c u rre n c e o f one mammal and two b ir d s to be o f to o few d a ta to su g g e s t
I
I
jf
I'
r
b
K'
th e s e to be s t a p l e s i n th e food o f th e o t t e r .
T h is s tu d y , r e v e a lin g
o c c u rre n c e o f 71 s c a t s c o n ta in in g f e a th e r s and 212 w ith mammals, in d ic a te d
t h a t th e o t t e r f e d upon th e s e anim als commonly.
Snakes o c c u rre d i n £ (0.1*%) o f th e t o t a l .
Four (0.7%) o f th e s e were
summer s c a t s .
i
i.
•
l-
-Ij-S—
By com paring th e rem ains o f c h a r a c t e r i s t i c bones (T able X) i n s c a ts
w ith r e f e r e n c e c o l l e c t i o n s i t was p o s s ib le to d eterm in e th e approxim ate
s iz e o f th e f i s h e a te n .
Remains in d ic a te d lit in c h t r o u t and 16 in c h
su c k e rs w ere f r e q u e n tly ta k e n .
■
L a g le r and O stenson (op c i t ) r e p o r t t r o u t
i n th e d i e t o f o t t e r s to a v erag e h i in ch es., su c k e rs 5 in c h e s .
No " le a v in g s " o r "caches" o f f is h e s were found to have been l e f t by
th e o t t e r .
A ll c a tc h e s seem t o be c o m p le te ly u t i l i z e d .
"Western p a in te d t u r t l e s (Chrysemys p i c t a ) were abundant i n th e a re a
b u t none a p p ea re d i n any s c a t .
An o t t e r was o b serv ed s n i f f i n g a t u r t l e
w hich was on a lo g i n th e w a te r w ith o u t d is tu r b in g i t •
On one o c c a s io n a golden eye duck (E u cep h ala) wing t i p and a few
f e a t h e r s .were found w ith o t t e r " s ig n " c lo s e b y .
D uring December, a
m u tila te d fr o g was found on th e ic e n e x t to a b e a v e r house w hich showed
" r e c e n t o t t e r a c t i v i t y , tr a c k s and " s ig n " .
Comparison o f Thompson and G ary Areas
The d ro p p in g s from th e Thompson a re a c o n ta in e d th e same c a te g o r ie s
o f a n im als and i n th e same o rd e r o f fre q u e n c y as th e com plete s c a t c o l l ­
e c t i o n (T ab les IIX and T l ) .
Those found i n 1122 d roppings w ere; F is h 1093
(97ollvO, in v e r te b r a te s 376 (33o£$), am phibians 137 (12 o2%) , mammals 116
(10.3$), b ir d s 1*3 (3.8$) and r e p t i l e s U (0.1*$). F o r G ary5S l a k e , i n v e r t e b r a t e s 190 ( 7 $ M S b a r e l y ta k e th e number one o c cu rren c e from th e
f i s h e s , 187 (7l.2$).
The same r e l a t i o n s c o n tin u e f o r th e o th e r groups:
Amphibians 116 (1*6.0$), mammals 96 (38.1$), b ir d s 28 (11.1$) and r e p t i l e s
I (0.1*$) f o r 252 s c a t s .
■
j
I
-1 9 -
O
Table IT .
1
A com parison o f th e s p e c ie s i d e n t i f i e d i n o t t e r s c a ts from H ? = Thompson Area
No. s c a t s :
i
I'
o
1 »
I
ICTTER
SPRING
SUMMER
FALL
8?
b36
53U
65
TOTAL'
1122
■
th o s e from G a ry 's L ake.
G ary' B ^
TCTTER
SPRING
SUMMER'
FALL
TOTAL
160
9 (9 0 .0 ) 190 175.4)
W l 2 0 .7 ) 13U (3 0 .7 ) 208 (3 9 .0 ) 16 (2U<»6) -TTTrrrorr 8 (66.6) m (71.3) 59 l o w )
INVERTEBRATES
3
(3 0 .0 ) 71 1 2 8 T
3
7
0
T
3
T
r
'
'2:
C16.7)
h
i
125.6)
25
U
3
.7
)
" T T lT in
60 (1 3 .5 ) 102 119.1)' 5 T tTHj
A quatic I n s e c ts
3 ( 1 . 2)
2 ( 1 .3 ) I ( 1.U )
9 ( 0, 8)
—— 5 ( 0 .9 ) i ( i.5 )
W ater Bug
. _3 C
. _3 .it) —— ———
78
(3 1 .0 )
5
(5
0
.
0)
2 (16.7) b8 (30.0) 23 (32.9).
59 ( 5 .3 )
A quatic B e e tle
3 ( 3«U) 23 ( 5.3) 29 ( 5.U) L ( 6.2)
3 ( 1 . 2)
-----------3 ( 1 .9 ) - - - - - - - U7 ( b . 2 )
Stone' F ly Nymphs'
6 ( 6*9) 2li ( 5.5) IU ( 2.6) 3 ( L.6)
9 ( 3 .6 )
9 ( 0 . 8) ________ 6 ( 3 .8 ) 3 ( b .3 )
2 ( 0.5)
7 ( 1.3)
Dragon F ly
—----- —
(1 9 .0 )
b8
2
20
.
0
)
6b ( 5.7) 3 (2 5 .0 ) 29 (1 8 . 1) l b (2 0 .0 )
( L.6)
Dragon F ly Nymphs
5 ( 5.7) 18 ( u.1) 38 ( 7.1)
6
6
0
.
0
)
(37.3)
9b
57 ( 5.D 3 (25.0) 62 (38.8) 23 (32.9)
( 3.1)
F re sh 'W a te r Shrimp I ( 1.1) 23 ( 5 .3 ) 31 ( 5.8)
9 ( 0. 8)
6 ( 1.U)
3 ( 0 . 6)
M illip e d e
—
12 (100J 118 (73.8) b7 (67.1) 10 TlOO.) 187 (7b=2)
' FISHES
HT(1 0 0 .) b27 197.9) 51b (9 6 .3 ) 65 ClOOJ 1093 197
T (T H )
86 (53.8) '27 (38.6) 10 (100.) 131 (52.0J
T ro u t '
21 (2b.l) 358(12.6) 3 2 ^ (6 .0 )1 5 (23.1) 123 (11.0) I 3 (25.0) bo (25.0) 30 (b2.9)
5 (50.0) 78 (31.0)
211
(1
8
.
8)
S c u lp in
22 (25.3) 82 (18.8) 96 (18.0) 11 (17.0)
108
(
9.6)
Squaw fish
6 ( 6.9) b8 (11.0) 53 ( 9.9) I ( 1.5)
2 ( 1 . 3 ). —--------- * — --------2 ( 0 . 8)
75 ( 6.7) —--------3 ( 0.6) 5 ( 7 .7 )
Columbia R. Chub
21 (2b.l) b6 (10.6)
----------I
(
0.6)
—---■
—
----------—
I
( O.b)
S u n fis h
33 (37=9) 280 (6b»2) bbo (82.b) b5 (69.2) 798 (71.1)
7b
(b6.3)
15
(21.b)
9
(90.0)
108
(b2.9)
10
(8
3
.3
)
Sucker '
b9 (56.3) 163 (37.b) 112 (21.0) 25 (38.5) 3b9 (31.1)
5 ( 3=1).------------ I (10.0)
7 ( 2.8)
b ( 0.7) 10 (15.b) b5 ( b.o) ' I ( 8 .3 )
W h ite fis h
9 (10.3) 22 ( 5.0)
(
6
.
1
)•
69
B ass"
b ( b.6) 30 ( 6.9) 35 ( 6.6) — - — - 75 ( 6.7)
(
8.0)
36
(
8.3)
28
(
5.2)
b
(
6*2)
P e rc h
7
b (33.3) 5l (31.9) 5 ( 7=1) 3 (30.0) 63 (25.0)
91 1.7) 10 (15A) 53 j J b Z L b (3 3 .3 ) "75 (b 6 .0 ) 32 (b 5 .7 ) 5 (50=0) 116 U 6 .0 T
S h in e r
10 (11.5) 2b ( 5.5)
5 ( 5.7) b2 ( 9 .6 ) 86 (1 6 .1 ) b ( 6 .2 ) 137 (12.WT
AMPHIBIANS
75 (b 6 .0 ) 32 (B T T )T (5 0 .0 ) 116 (boTo)
5 ( 5.7) U2 ( 9.b) 8b (1 5 .7 ) 3 ( b.6)' 13b (i i oTT b (3 3 .3 )
Erog
----------2 ( 0 . 8)
2 ( 1 .3 ) — ■
5 ( o.b)
b ( 0 .7 ) I ( 1.5)
Salam ander
T T OJi)
T T 0.6)
~b ( O .b) ■ ~~~—
b ( 0 .7 1
REPTILES
1 ( oTET
I ( 0.6) T T oT b T
b ( 0 .7 )
Snake
28
(lO T
2 ( 1 6 .6 b 23 (IU=U) 3 ( b .3 J 3 ( 3»b) 17 ( 3 .9 ) 22 ( U.l)" T ( 1=5)
BIRDS
—
——
13
( 5=2]
T8T3T 12 ( 7 . 5 )
T T O T
9 ( i* 7 ) —
7TTT6)
----10
( b.o)
Unknown
6 ( 3 . 8) 3 ( b.3)
(.8.3)
22 ( 2 . 0)
7 ( 1 . 6) 11 ( 2.1) 1 ( 1 5)
DucSc
3 ( 3.b)
'—
—
5
( 2.0)
5 ( 3.1)
5 ( o.b)
2 ( o.b) — — —
3 ( 0.7)
Grebe
9
6
(TTTT
2 (16. 6) 53"(33.1) 39 (55.7) 2 (20.0)
6 ( 6 .9 ) 3TTHT qT 65 (12.2) 10 (l5.b) 116 (1 0 .3 ) _________
MAMMALS
( 1 .2 )
3
2 (1=3)
b ToT bT 1
8-3)
3 TOTH)
1 \ 0. 2)
(13=9)
Unknown
35
95 ( 8.5) .1-4 8.3) 11 ( 6.9) 22 (31.b) I (10.0)
8
O tte r ( t r a c e )
5 ( 5.7) 31 ( 7=1) 50 ( 9 .b ) 9 (13.8)
( 3 .2 )
7 ( b.b) I ( i .b )
2 ( 0 .2 ) ■ — i -----— 1 ( 1 .5 )
1 ( 1 . 1)
Beaver"
(1 8 .7 )
b7
lb ( 1 .2 )
---------- - 30 (18.8) 16 (22.9) I (10.0)
3 ( 0.7) 11 ( 2.
M uskrat
2
( 0. 8)
2 ( 1.3)
Meadow Mouse
I
( o.b)
I 0 .6)
I
Shrew
( o.b)
I 0 .6 )
I ( 6. 1)
—
— ————— I ( 0 .2 )
Mink
I ( 0 . 1)
I ( 0*2) —-------—Ground s q u i r r e l
'T.' -
(
-2 0 -
A t G a r y 's , th e f i s h o c c u rrin g i n th e h ig h e s t p e rc e n ta g e o f th e s c a ts
was th e t r o u t 131 (52.0% ).
T ro u t ap p eared m o s tly i n w in te r (66.7%) and
f a l l (100%), l e a s t i n th e summer (38.6% ).
On Thompson a r e a , t r o u t ra n k e d
f o u r th and m a in ta in e d th e same s e a s o n a l tr e n d found a t th e o th e r s tu d y
a r e a , i . e . , h ig h e s t i n w in te r (2l|..l%) and f a l l (23*1%), lo w e st i n summer
(6.0% ).
The ra n k in g f i s h a t th e Thompson a r e a was s u n fis h 798 (71,1%)
w ith a h ig h i n summer (8 2 .1 $ ) and low i n w in te r - (37.9% ).
n o t c o l l e c t e d o r r e p o r te d t o o c c u r i n G ary’ s l a k e .
T his f i s h was
S uckers were second
i n o c c u rre n c e f o r b o th Thompson 3h9 (31.1%) and G ary’s 108 (lj.2.9%).
They
showed th e same s e a s o n a l tr e n d f o r th e r e s p e c tiv e a r e a s ; h ig h i n w in te r
(5 6 .3 and 83.3%) and low f o r th e summer (2 1 .0 and 2 1 .1 $ ).
T h ird p la c e f o r
G ary’ s was th e s e u lp i n , o c c u rrin g in 78 (31.0% ) and showing g r e a t e s t f o r
summer (!$.9% ) and f a l l (50.0% ).
was a ls o th e s e u lp in 211 (l8 .8 % ).
At Thompson’ s th e t h i r d im p o rta n t f i s h
I t showed ab o u t e q u a l r e l a t i o n s
th ro u g h o u t th e s p r in g (18.8% ), summer 0.8.0%) and f a l l (17.0%) b u t in c r e a s ­
ed i n w in te r (25.3% ).
63 (25.0% ).
The f i s h o c c u rrin g f o u r th a t G ary’s was th e s h in e r
These were p r e s e n t i n a t l e a s t 30% o f th e s c a ts f o r th e
w in te r , s p rin g and f a l l w ith lo w e s t r e p r e s e n ta tio n d u rin g th e summer
(7 .1 % ).
T his low tr e n d f o r s h in e r a ls o a p p e a rs f o r th e same p e rio d i n th e
Thompson a r e a (1.7%) a lth o u g h i t s o c cu rren ce a t no seaso n approached t h a t
a t G ary’ s .
S quaw fish, b a ss and p e rc h were e n t i r e l y a b s e n t from any a n a ­
ly z e d s c a t s c o lle c te d from G ary’ s a re a and th e o n ly o ccu rren c e f o r a
Columbia, r i v e r chub i n 2 s c a ts and s u n fis h i n I were re c o rd e d f o r th e
s p ra n g .
E vidence s u g g e s ts th e s e w ere p ic k e d up e lse w h e re .
F o r Thompson,
Ii
:!
th e sq u aw fish had a t o t a l o c cu rren c e o f 108 (9*6$)„
I t was g r e a t e s t f o r
s p r in g ItS (ll„0 % ) and summer 53 (9<.9%)j lo w e st f o r f a l l I ( l 65%).
C ol­
um bia r i v e r chub t o t a l e d 7 5 .( 6 .7 # ) ; o f th e s e 21 ( 2 lu l# ) were i n th e
w in te r , it6 ( l 0 e6#) i n s p r in g and 3 (0 .6 # ) in summer.
Of a l l ap p earan ces
;s
o f b a s s 69 ( 6 .1 # ) , s p r in g 30 (6 .9 # ) and summer 35 (6 .6 # ) were m ost prom i­
n e n t fo llo w e d by it (lto6#) f o r w in te r and e n t i r e l y a b s e n t d u rin g th e f a l l .
P e rc h were found i n 75 (6 .7 # ) s c a t s ; s e a s o n a l usage ran g ed from 5«2 to
8 .3 # .
T o ta l w h ite f is h o c c u rre n c e was lt5 (lt®0#).
These ap p eared m o stly
i n th e f a l l 10 (l5«lt#) and w in te r 9 (1 0 .3 # ) fo llo w e d b y s p rin g 22 (5 .0 # )
and th e n summer it ( 0 .7 # ) .
T h is same tre n d ap p eared f o r Gary1S ta k e b u t
to o few d a ta a re a v a ila b le f o r d e f i n i t e c o n c lu s io n s .
Only 7 (2 .8 # )
a p p e a re d , w ith f a l l I (1 0 .0 # ) and w in te r I (8 .3 # ) h i g h e s t , fo llo w e d by
s p r in g 5 (3 .1 # ) and none f o r summer.
I n v e r te b r a te s a re 2 to 3 tim e s g r e a t e r in p e rc e n t o ccu rren c e a t
G ary’ s th a n a t Thompson a re a f o r a l l seaso n s b u t no seaso n h ad l e s s th a n
20# f o r e i t h e r a r e a .
i
The m ost pro m in en t a t G ary’s w e re: F resh w a te r
,1
shrim p 9lt (3 7 .3 # ) , a q u a tic b e e tl e 78 ( 3 1 .0 # ) , " a q u a tic in s e c ts " 71 (2 8 .2 # )
!I
and d ragon f l y nymph i+8 ( 1 9 .0 # ) .
A t Thompson a r e a " a q u a tic in s e c t s " were
1:
p r e s e n t i n 170 ( l5 .2 # ) o f th e t o t a l ; a l l o th e rs were re p re s e n te d l e s s th a n
6# e a c h .
S to n e f ly nymphs ( P le c o p te ra ) were re p r e s e n te d in a l l se a so n s a t
I
Thompson b u t o n ly d u rin g th e s p r in g a t G ary’ s .
:!
F ro g s ap p eared i n L6.0# o f th e c o l l e c t i o n a t G ary ’s and w ere re c o rd e d
f o r 3 3 .3 # o r more f o r a l l s e a s o n s .
The Thompson o ccu rren c e was 1 1 .9 #
showing h ig h e s t f o r summer l5®7# and lo w e st i n f a l l I u 6#.
O
Salam anders
:!
1!
-2 2 -
were ta k e n a s a t r a c e i n b o th a r e a s .
O
H afc and mammal rem ain s mere i n 96 (3 8 . 1«
( 1 0 .3 « a t ttom pson.
s c a t s a t G a ry 's and 116
E x clu d in g t r a c e s o f o t t e r h a i r th e f i g u r e s a r e 62
(2k.6%) and 22 ( 2 .0 * ) .
M uskrat was th e m ost numerous i n s c a t s c o n ta in in g
h a i r found i n b o to a r e a s .
Of th e t o t a l 1,7 (1 8 .7 * ) c o n ta in in g m u sk rat h a i r
a t G a r y 's , 30 (1 8 .8 * ) were i n th e s p r in g ,. 16 (2 2 .9 * ) i n summer, I ( 1 0 . 0* )
i n f a l l and a b s e n t f o r w in te r .
Ht
H e Thompson a r e a s c a ts w ith m u sk rat h a i r
( 1 . 2* ) , was h ig h e s t f o r summer 11 ( 2. 1*) fo llo w e d by s p rin g 3 ( 0 . 7*).
and a b s e n t i n b o th w in te r and f a l l *
B e a re r o c c u rre n c e was 8 (3 .2 * ) f o r G a ry 's and o n ly 2 (0 . 2*) f o r th e
Hiompson a r e a .
A ll usage a t G a ry 's was i n s p rin g 7 (It.I,*) e x c e p t I
(I-W ) i n s u m e r .
and f a l l .
t)
Usage
At Thompson i t was re c o rd e d i n I s c a t each f o r w in te r
Cf
o th e r mammals f o r b o th a re a s was to o i n s i g n i f i c a n t
f o r com parison (T able 2) .
Of th e 28 (11. 1* ) s c a ts from G a ry 's h av in g f e a t h e r s , 23 (I),.!,* )
o c c u rre d i n th e s p r in g , 3 (it.3 * ) i n summer and 2 (1 6 .6 * ) i n w in te r .
T h ir­
te e n (5 .2 * ) were o f unknown i d e n t i t y , 10 (!,.0*) w ere duck and 5 ( 2 . 0* )
g re b e s .
A U g re b e s w ere re c o rd e d f o r th e s p r in g p e r io d .
Duck ap p eared
i n 6 (3 . 8* ) s p rin g s c a t s , 3 tit.3 * ) i n summer, I ( 8 . 3*). i n w in te r and none
in fa U .
S p rin g I 7 (3 .9 * ) and summer 22 (it.I * ) s h a re d ab o u t e q u a l im­
p o rta n c e f o r f e a t h e r o c c u rre n c e re c o rd e d f o r Thompson a r e a .
From t h i s
a r e a 16 ( I . Il*) were c l a s s i f i e d a s unknown f o r th e t o t a l k3 (3 . 8* ) .
Twenty-two (2.0*) were duck and 5 (0.W ) grebes.
Ducks appeared in I l
(2.1*) sca ts during the summer, 7 (1.6*) in spring, 3 (3.1,*) in winter
D
and I
in f a l l .
summer 2 (OoLif) .
G rebes were re c o rd e d f o r s p rin g 3 (OarIf0) and
The in c id e n c e o f f e a t h e r o c cu rren c e was g r e a t e s t d u rin g
June a t G ary’s , w hereas i t was h ig h e s t d u rin g A ugust a t Thompson a r e a .
R e p tile s ap p eared i n U (0<>7%) s c a t s , a l l from summer c o l l e c t i o n s a t
Thompson and I (Oa6%) f o r th e s p rin g a t G ary’s .
Tapeworm In c id e n c e
Tapeworm p r o g l o t t i d s o c c u rre d i n s c a t s from b o th a r e a s .
They were
i n 12 (8.6% ) o f th e A p ril s c a t s w ith 11 (l6«2%) f o r Thompson and I (1.1;%)
f o r G ary’s? 17 (9»7%) f o r Mays 17 (11.6%) and z e ro ; 17 (6.1%) f o r Ju n e ,
16 (7.2% ) and I (1.7% ); l i (5*7%) f o r 'J u ly , ,11 (3 . 1%) and 3 (9.1% ); 20
(7.2% ) f o r A u g u st, 20 ( 7 . 8%) and z e r o .
S c a ts c o n ta in e d from 2 t o 76 p ro ­
g l o t t i d s which ra n g e d from 1 /8 to Ig- in c h e s .
A c o l l e c t i o n o f 20 squaw fish
from th e P le a s a n t V a lle y F is h e r r i v e r , a d ja c e n t t o an o fte n u s e d o t t e r
l a t r i n e , re v e a le d 8 to c o n ta in l a r v a l tapeworms i n t h e i r body c a v i t y . These w ere found t o a l e s s e r e x te n t i n s h in e r and p e rc h .
The p r o g l o t t i d s
and l a r v a l s ta g e s were b o th i d e n t i f i e d as L ig u la i n t e s t i n a l i s b y th e
A g r ic u ltu r a l R esearch C e n te r, B e l t s v i l l e , M aryland.
W ardle (1935) m entions
t h i s tapeworm as f r e q u e n t i n f i s h e a tin g b i r d s .
DISCUSSION
The d a ta in d ic a te t h a t th e fo o d o f th e o t t e r v a r ie s w ith in r e s t r i c t e d
l i m i t s from one a r e a t o a n o th e r .
n o t re a d ily in te rp re te d .
The re a so n s f o r th e s e d if f e r e n c e s a re
I n some c a se s i t seems to be a case o f a v a i l a ­
b i l i t y o f p re y (num bers) b u t i n o th e rs t h i s i s n o t r e a d i l y a p p a r e n t.
It
seems obvious t h a t th e h a b its o f c e r t a i n f i s h e s would make them more
6
v u ln e r a b le th a n o th e rs i r r e s p e c t i v e o f t o t a l p o p u la tio n s .
I t fo llo w s
t h a t th e l i m i t e d s a m p lin g .o f f i s h p o p u la tio n s b y g i l l n e t t i n g , e l e c t r i c
sh o c k in g , and f i s h i n g d id n o t n e c e s s a r i l y in d ic a te th e r e l a t i v e abundance
o f v u ln e ra b le p o p u la tio n s .
The predom inent f i s h , s u n f is h (71.1% o f s c a t s
from Thompson), e a te n by th e o t t e r was n o t ta k e n i n any g r e a t numbers by
sa m p lin g .
I t was n o te d w h ile w alk in g th e la k e sh o re s t h a t s u n f is h were
ab u n d an t c lo s e to th e w a te r ’ s edge d u rin g th e s p rin g and summer s e a s o n s .
S e le c t iv e a n g lin g i n a few o f th e s e p la c e s d id in c r e a s e the s u n f is h c a tc h
b u t s t i l l n o t in p ro p o r tio n to t h e i r o ccu rren c e i n s c a t s .
I n a l l p ro b a ­
b i l i t y th e h a b its o f th e s u n f is h , c o rin g a t l e a s t some p e r io d s , make them
more a v a il a b le to th e o t t e r .
One o b s e rv a tio n o f two o t t e r i n a s m a ll la k e
showed t h e i r manner o f "h u n tin g " to be t h a t o f c i r c l i n g th e la k e r a t h e r
c lo s e to th e sh o re l i n e .
Qn th e o th e r h a n d , th e h ig h in c id e n c e o f s u n fis h
i n th e s c a ts a t Thompson c o u ld p o s s ib ly in d ic a te a p re fe re n c e f o r t h i s
s p e c ie s b u t a t G a ry 's where s u n f is h were a b se n t o t t e r were e q u a lly abund­
a n t and d iv e r te d t h e i r a t t e n t i o n tow ards o th e r p r e y .
The p o p u la tio n s o f b a s s , t r o u t and s h in e r a s in d ic a te d b y sam pling
I
:i
!’
i,
w ere a ls o lo w er th a n i s su g g e ste d by t h e i r o c c u rre n c e in s c a t s .
P
I n c o n t r a s t to th e f i s h e s above, th e sq u aw fish and Columbia r i v e r
chub d id n o t o ccu r as f r e q u e n tly i n s c a ts a s .th e I r a p p a re n t abundance
I
i!
i n d i c a t e d by f i s h i n g i n p o o ls a d ja c e n t to o fte n u s e d l a t r i n e s ' would sug­
g e s t.
One. c a tc h f o r 30 m in u tes o f f is h in g y ie ld e d 20 sq u aw fish .
At a
la k e n e a r o t t e r l a t r i n e s , 3 h o u rs o f f i s h i n g r e s u l t e d i n a c a tc h o f over
ii
D
-25100 sq u a w fish .
These f i s h e s were o n ly r e p r e s e n te d i n 1 6 .3 # o f th e t o t a l
s c a ts .
W h ite fis h were ta k e n i n deep w a ter g i l l n e t s e t s and in g r e a t e r p ro ­
p o r ti o n th a n t h e i r in c id e n c e i n d ro p p in g s .
S c h e ffe r (1933) r e p o r te d th e
c a p tu r e o f o t t e r (L u tra c a n a d e n s is ) i n c ra b p o ts s e t in 60 f e e t o f w a te r.
1S
Numbers o f p e rc h c au g h t by f i s h i n g and g i l l n e ts gave an in d ic a tio n o f
g r e a t e r o c cu rren c e th a n s c a t a n a l y s i s .
From 52 s c a ts c o lle c te d on th e
lo w er Thompson Lake5 21 had p e rc h rem ains (1*0.1*#) and 16 (3 0 .8 # ) had su n fis h .
I n th e u p p er Thompson Lalce5 p e rc h were i n 21 o f 226 s c a ts (9 .3 # )
and s u n f is h i n 205 s c a t s (9 0 .7 # ) .
The- re a so n s f o r th e in c r e a s e o f p e rc h
i n th e d i e t from one end o f th e s e la k e s to th e o th e r i s d i f f i c u l t t o
e v a lu a te .
I n some in s ta n c e s th e r e does ap p ear to be a d i r e c t c o r r e l a t i o n b e ­
tw een r e l a t i v e abundance and u t i l i z a t i o n .
The c a tc h o f s c u lp in s by
sh o ck in g seemed p r o p o r tio n a te to th e o c cu rren c e i n s c a ts a s d id th e
“
numbers o f su c k e rs c au g h t i n g i l l n e ts ( Table I)-,
O tte r p r e d a tio n on f o r b e a r e r s seemed to be i n r e l a t i o n t o a v a i l a ­
b ility .
G ary’s Lake had a h ig h e r in c id e n c e o f b e a v e r and m u sk rat th a n
Thompson (T able I I ) and th e d e g re e o f u t i l i z a t i o n was h ig h e r .
M uskrat
rem ain s f i r s t a p p ea re d i n th e s c a t s d e p o s ite d d u rin g A p ril f o r b o th a r e a s .
;!
I'
1I
!<
A t G ary 1S5 s c a t s w ith m u sk rat re a c h e d a peak i n J u n e 5 o c c u rrin g i n ll*.
E vidence o f m u sk rat was h ig h e s t d u rin g August a t Thompson a r e a 5 a p p e a rin g
in 5 s c a ts .
The predom inant o ccu rren c e o f m u sk rat rem ain s i n th e s p rin g
and summer s u g g e s t th e v u l n e r a b i l i t y o f t h i s s p e c ie s when t h e i r numbers
t
I
-
26 -
e x ceed th e s e c u r i t y le v e l s u n d e r p r e v a ilin g c o n d itio n s (E rrin g to n , 19h3and 19h6) .
Of th e 8 s c a t s c o n ta in in g b e a v e r a t G a r y 's , 5> o c c u rre d d u rin g A p r il,
2 i n May and I f o r A ugust.
The two f o r Thompson's c o n s is te d o f one each
f o r f a l l and w in te r .
CONCLUSIONS AND RECOMMENDATIONS
The w a te rs o f th e Thompson la k e re g io n a re h e a v ily p o p u la te d w ith
f i s h e s n o t p a r t i c u l a r l y so u g h t b y fis h e rm e n .
h ig h p e r c e n t o f th e d i e t o f th e o t t e r .
These f is h e s c o n s t i t u t e a
F is h in g p re s s u re i s l i g h t .
I t is
th e o p in io n o f th e w r i t e r t h a t th e f a c t s do n o t j u s t i f y th e c o n c lu sio n
t h a t o t t e r c o n s t i t u t e a menace t o th e s p o r t f i s h i n g o f th e a re a a lth o u g h
th e y may do some damage l o c a l l y .
- . ^ le c^ a in d i c a t e t h a t o t t e r ta k e some m uskrat and b e av e r p a r t i c u l a r ­
l y i n a re a s o f h ig h p o p u la tio n s b u t a modern i n t e r p r e t a t i o n o f p r e d a to r -
I;
p re y r e l a t i o n s h i p s su g g e s ts t h i s can n o t be i n t e r p r e t e d a s a tr u e popu­
l a t i o n d e p re s s a n t.
I t i s more s u g g e s tiv e o f to p h eav y v u ln e ra b le popu­
l a t i o n s r e s u l t i n g p e rh a p s from i n s u f f i c i e n t h a r v e s t s .
I t would a p p ea r
t h a t , m uskrat and b e av e r tr a p p in g i n th e a re a sh o u ld be in c r e a s e d .
The numbers o f o t t e r do n o t a p p ea r s u f f i c i e n t to w a rra n t an open
season.
There i s th e p o s s i b i l i t y how ever, t h a t a lim it e d open sea so n
m ight s tim u la te an in c r e a s e i n re p ro d u c tio n and s u r v iv a l i n t h i s popu­
l a t i o n and c r e a te a s e l f im posed p r o te c tio n by r e s i d e n t s on an an^mni
now s u b j e c t t o a c ts o f v a n d alism .
I,
4
The need f o r a l i v e tra p p in g and m arking s tu d y to d eterm in e home
I
D
Ii
r
ii
i1
—
27 “
2 )
ra n g e seems a p p a re n t to a id i n ' a b e t t e r u n d e rs ta n d in g and management o f
,
t h i s a n im a lo Such in fo rm a tio n w ould p ro v id e d a ta f o r management u n i t s ,
p o p u la tio n e s tim a te s , e t c .
F eeding ex p erim en ts w ith c a p tiv e s would r e v e a l th e v a lu e , one way o r
th e o t h e r , o f u s in g d ro p p in g s a s an i n d i c a t o r o f th e number o f an im als i n
an a r e a .
These ex p erim en ts c o u ld a ls o s e rv e as a fo u n d a tio n f o r d e t e r -
. m ining th e r e l a t i o n s h i p betw een u n d ig e s te d rem ains found i n s c a ts and th e
■number and k in d s o f anim als e a te n th u s p ro v id in g a b a s is f o r more a c c u r­
a te e v a lu a tio n s o f s c a t a n a l y s i s .
SUMMARY
1.
A food h a b its s tu d y b y s c a t a n a ly s is was conducted i n th e
Thompson la k e s re g io n o f L in c o ln C ounty, M ontana, to h e lp e v a lu a te th e
econom ic s t a t u s o f th e o t t e r .
2.
O tte r l a t r i n e s were lo c a te d b y w alk in g th e sh o re l i n e s o f la k e s
and s tre a m s 5
were d is c o v e re d on f a l l e n t r e e s , b e a v e r houses and th e
sh o re .
3.
O tte r s c a t s were e a s i l y d is tin g u is h e d b y s i z e , sh a p e , and o d o r.
A - t o t a l o f 2209 were c o lle c te d betw een A p r il, 1932, and May, 1933.
Ap­
p ro x im ate d a te o f d e p o s it was d eterm in ed f o r 137b which w ere a s s ig n e d to
w in te r , s p r in g , summer and f a l l .
i
s tu d y .
;
b.
, f
The lim ited use of e le c tr ic shocking, g i l l net se ts and fish in g
were employed in an attempt to obtain the r e la tiv e abundance o f fish e s in
the various waters.
*<
These c o n s t i t u t e d th e b a s is f o r t h i s
'
An ind ication of fur bearer abundance was afforded
S c a ts w ere a n aly z e d i n a d ry s t a t e .
I
Each was b ro k en a p a r t i n a
c u ltu r e d is h w ith d is s e c tin g n e e d le and tw e e z e r.
The com plete s c a t was"
s e a rc h e d f o r i d e n t i f i a b l e rem ain s o f ite m s i n th e d i e t .
i d e n t i f i e d by com parisons w ith re f e r e n c e c o l l e c t i o n s .
These were
H a ir i d e n t i f i ­
c a tio n s were r e s t r i c t e d to f u r b e a r e r s ( o t t e r , b e a v e r, m u sk ra t, m ink);
f e a t h e r s t o A natidae and g re b e s .
A ll s c a ts and r e f e r e n c e c o lle c tio n s a re
a t Montana S t a t e C o lle g e .
6.
D a ta a re e x p re ss e d as p e rc e n t o c c u rre n c e b y se a so n s w hich was
c a lc u la te d by d iv id in g th e number o f s c a t s f o r a sea so n i n t o th e number
\
o f o c c u rre n c e s o f an ite m .
7.
D ata f o r two s e p a ra te d a re a s (Thompson and G ary) a re compared.
8.
F o r th e e n t i r e y e a r and f o r b o th a re a s f i s h rem ain s were
i d e n t i f i e d m ost f r e q u e n tly , a p p e a rin g i n 1280 (93»2%) o f th e s c a t s .
In ­
v e r t e b r a t e s were re c o rd e d f o r 5>66 (i|1.2% ), am phibians 2j?3 (1 8 . 1$ ) , mammals
212 ( 1 5 .1 $ ) , b i r d s ' 71 (5 .2 # ) and r e p t i l e s 5 ( 0 1 $ ) .
9«
C o n sid e rin g a l l s c a t s , s u n f is h o c c u rre d i n 5 8 .2 # , su c k e r 3 3 .3 # ,
s c u lp in 21<>0#, and t r o u t 1 8 .5 # .
t a b lis h e d f o r th e Thompson a r e a .
This same o rd e r o f im p o rtan ce was e s ­
Gary’ s la k e was: t r o u t 5 2 .0 # , s u c k e r
lj.2o9#, s c u lp in 3 1 .0 # and s h in e r 2 5 .0 # .
10.
Dragon f l y nymph, a q u a tic b e e t l e s and f r e s h w a te r shrim p a p p e a r­
e d i n s c a ts c o n s i s t e n t l y b u t seldom made up an a p p re c ia b le p e rc e n t o f th e
s c a t.
*
I t was m ost common to f i n d 1 -5 o f th e s e i n a d ro p p in g .
11.
Frogs were found to be a p ro m in en t p a r t o f th e d i e t and.w ere
found th ro u g h o u t a l l s e a s o n s .
12.
M askrat o c c u rre d i n
o f t o t a l s c a t s b u t was p r e s e n t i n 18.7%
o f th e c o l l e c t i o n a t G ary’ s la k e and pred o m in an t d u rin g s p rin g and summer.
The h ig h e s t In c id e n c e was i n Ju n e , o c c u rrin g i n l k s c a t s .
B eaver ap p eared
i n 10 o r 0.7% o f a l l s c a ts w ith 8 o c c u rrin g a t G a ry 's and 2 f o r th e
Thompson.
13.
The d a ta s u g g e s t a v a i l a b i l i t y t o be im p o rta n t i n d e te rm in in g
th e fo o d h a b i t s o f th e o t t e r .
Ol1.
Iapew am p r o g l o t t i d , M g a la i n t e s t i n a l i s , were found i n s c a t s
from b o th a r e a s .
LITERATURE CITED
C rabb, ¥ . D.
1*1.
Food h a b i t s o f th e p r a i r i e s p o tte d skunk i n s o u th -
e a s t e r n Iow a.
E r r in g to n ,? .! ..
J o u r . Mamm., 22;3U9”36I|-«
1*3.
t o a n a ly s is o f m ink p re d a tio n upon m u sk rats i n
n o r t h c e n t r a l V. S .
,
!9 ^ 6 .
Iow a A g ric . Bxp. S t a . , R es. B u ll. Mo. 320= 797-*U .
P r e d a tio n and v e r t e b r a t e p o p u la tio n s .
Q u a rt. Rev.
B i o l . , 21sll|.L-177, 221-2US>*
F e r r e l , 0 . M ., H. R . Leaoh and D. F . T i l l o t s o n .
coyote i n C a l i f o r n i a .
F is h e r, E . M .
1*0.
1*3.
Food h a b its o f th e
C a l i f . F is h and Game., 39=301-3U l.
Batty l i f e o f a s e a o t t e r pup.
J o u r . H a m ., 21=
132-137.
L a g le r , K. F . and B. I . O sten so n .
i n M ichigan.
L ie rs , E . B.
1*1.
1*2.
E a r ly s p rin g fo o d o f th e o t t e r
J o u r , m i d l i f e M g t., 6t2bh-2$b>>
Motes on th e r i v e r o t t e r (L u tra c a n a d e n s is ) ■ J o u r .
-
30-
Hirame, 3 2 :1 -9 .
M ath ia k , H. A.
1938.
A key to h a i r s o f th e mammals o f so u th e rn M ichigan.
J o u r . W ild lif e H g t., 2 :2 3 1 -2 6 8 .
M ayer, W. 7 .
I
1932.
The h a i r o f C a lif o r n ia mammals w ith keys t o th e d o r-
s a l g u ard h a i r s o f C a l if o r n ia mammals.
M u rie , 0 . J .
1 9 i0 .
; . S c h e f f e r , V. B,
N otes on th e s e a o t t e r .
1933.
Araer. H id . N a t., U8 :I|.80-3l2.
J o u r . Mamra., 2 1 :1 1 9 -1 3 1 .
O tte r s d iv in g to a d ep th o f s i x t y f e e t .
Jo u r.
Hamm., 3U$233«
S c o t t , T. G.
19l].l.
Methods and com pu tatio n i n f e c a l a n a ly s is w ith r e f e r ­
ence to th e r e d f o x .
W ard le, R . A.
1933*
Iowa S ta te C o ll. J o u r . S c i . , 1 3 :2 7 9 -2 8 3 .
F ish-tapew orm .
The B io l. Bd. Canada, B u ll. It3.
108553
<■& ■■■-"V-V
$ 252
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