Food habits of badgers (Metes metes) in an arid habitat
A.
RODRIGUEZ AND
M. DEEJBES, CSIC, Estacidn Biolégica de Doflana, Apdo. 1056,
41080 Seville, Spain
Introduction
The European badger (Meles metes) is widely distributed in the Palaearctic, mainly associated to
woodland and hilly areas (Neal, 1976). It is absent from North Africa and most of the Arabian
region, as thesouthern boundary of its range runs through Palestine and Iran (Corbet, 1978). This
limit coincides quite well with the border between semi-arid and hot arid climate reons in the
Middle East (Cleveland, 1988). Hence, aridity could be recognized as a limiting factor of badger
distribution, and observations on the natural history of the species in arid and sub-arid
environments attain particular interest.
Many of the surveys on the food habits of the badger have been carried out in temperate
Eurosibcrian environments (Neal, 1986), where it is largely considered as an earthworm specialist
(Skoog, 1970; Kruuk & Parish, 1981; Henry. 1983; Neal, 1988), although it is able to take a large
variety of food. The aim of this note is to report summer foods of the badger in a sub-arid area of
south-east Spain.
Study area and methods
In September 1981 and July 1987, a minimum of 205 faeces from 6 (more than 90) and 13 (more
than 115) badger dung sites, respectively, were collected in the valley of the River Aguas, near
Sorbas (Almeria, SE Spain; 37° 6’ N, 2° 3’ W). This region is amongst the most arid in Europe, with
annual average temperature of 18 °C and 230mm of annual average rainfall. Rain is absent during
summer, except for some very occasional torrential storms (monthly rainfall averages less than
5 mm in these months; Font, 1983). The soil is poor, being able only to support scarce xerophitic
vegetation. However, water is locally available enabling the existence of some little orchards,
irrigated crops and vineyards. Samples for this study come from the proximity of one of such sites.
Faeces were dried at 40°C and weighed. Volumetric estimations of each type of prey were made
for each dung site (1987 faeces) or all of the material (1981 faeces) following the “weight of
undigested matter” method (Lockie, 1959). In order to obtain a rough estimate of ingested fresh
weights, correction factors proposed by Lockie (1961) for martens (Martes martes)—also an
omnivorous rnustelid—were used, as we do not know of similar factors for badgers. However, we
introduced some minor changes: factor 5 was used for all arthropods (imagos), 12 for all larvae,
and 40 for cultivated fleshy’fruits. This lastfactor was estimated from the proportion between fresh
and dry weights of fruit peels. Samples of faeces of all dung sites were watered down and examined
at 40 x magnification, searching for earthworm chaetae.
Results
Results are shown in Table L Arthropods, mainly insects, are the only prey item occurring in all
19 sites. They represent 44% of total volume, but only account for 11% of estimated total biomass
ingested. Fruits, all of them cultivated except Ephedra, occur in 71 % of the sites and reach 76% of
estimated ingested biomass. They appear as the summer staple food of badgers in. the area.
Vertebrate items occur only in five sites, corresponding to one mammal, one bird, two reptiles
and one amphibian species. Estimated fresh weights consumed from these prey suggest that a
single individual was eaten each time, except perhaps in the case of snakes and toads. None of the
vertebrates equals 5% of ingested biomass. Soil was found in faeces in 89% of sites (usually earth
accounting for <10% of excrement weight) but no earthworm remains were detected.
Trophic diversity within sites (H’, Shannon index) increases when fruit proportion decreases
(Spearman rank correlation, r=0927, P< 0005), suggesting that badgers eat mainly fruits when
these are available. An increase in the proportion of fruits in the diet was noted throughout the
summer, from 67% of ingested biomass in July to 87% in September. At the same time, trophic
diversity decreases 23% from JuLy to September (Table I).
Fruits occur in faeces as they ripen: late ripening fruits such as grapes and almonds were only
found in September samples, while plums and pears appeared in July.
Arthropods belonging to at least nine taxonomic orders were found, all of them consumed in
low quantities. In 85% of the sites, the arthropod remains belonged to at least four different orders.
Arthropods were the major component of diet diversity, as relative diversity of evenness (Pielon,
1977) within each site was positively correlated with the percentage of biomass of arthropods
(r=08, P<001).
Discussion
Feeding of badgers in Sorbas seems to depend largely on cultivated fruits, whose existence in the
area is restricted to the scattered and scarce water-available sites, Also, in Jordan, Syria and
Lebanon the species is confined to the fertile regions, although in Israel it is widely distributed in.
the central and northern parts of the country, with 300 mm annual rainfall, and it has been
reported even in areas with only 120mm precipitation (Long & Killingley, 1983).
The badger is a fairly heavy carnivore which must need a quite important daily amount of food
for maintenance and reproduction. Henry (1983) estimates a minimum daily food intake of 530g.
Moreover, as said by Neal (1.986), “it is primarily a forager, not a hunter, (for which) it may take
many hours before sufficient food has been collected”. Hence, the presence of an abundant food
supply all around the year may be an important factor influencing its distribution. Kruuk
(I 978a, b) suggests badger density would be determined by food distribution (in his case, patches
of earthworms influencing territory size of the clans) and food abundance (influencing clan size).
Probably arid regions, except when cultivated, do not produce enough clumped food to allow the
existence of badgers.
In our study area, nothing is known about distribution and abundance of earthworms (A.
GarcIa, pers. comm.), but if they exist, climate probably prevents their activity, at least in summer.
Climate also precludes the extensive culture of cereals. Thus, the two prevailing food sources of
badgers in agricultural areas of northern Europe (Kruuk & Parish, 1985; Skinner & Skinner, 1988)
are not available in Sorbas. Vertebrate prey are scarce, except perhaps reptiles, whose diurnal
habits are likely to reduce their availability for badgers. Therefore, only arthcopods and cultivated
fruits seem to be abundant foods. Both have been also reported as the main food items of badgers
in undisturbed Mediterranean habitats during the summer-autumn season (Ciampalini & Lovari,
1985).
TABLE I
Summer diet of badger expressed as biomass
Biomass (g)
Prey items
July
September
975-7
Oryctolagus cuniculus
Lagomorphs
Turdus merula
4-98
66-2
Birds
0-33
Colubridae
Lacertidae
Reptiles
558-0
82-8
Bufo bufo
4384
3-27
Amphibians
Myriapoda
Chilopoda
Escorpiones
Isopoda
Orthoptera
Coleoptera (imBgos)
Coleoptera (larvae)
Lepidoptera (larvae)
Others
Arthropods
Plums
Pears
Melons
Figs
Apricots
Grapes
Almonds
Ephedra major
Fruits
Maize
223
2-4
988
I 29-6
I66
246
5263
6727
4451
23-0
227
56-7
11-3
ff3
11-3
1124
52765
1475-0
131-5
3940
17017
1134-5
453&O
1906
95-3
76-23
153-7
Cereals
0-78
Eggs
98-6
Carrion
80-2
H’
% Biomass
Whole summer
0-7785
0-50
0-41
0-5974
To judge from the diversity of groups of ingested arthropods (which have small size and
probably are sparsely distributed), they must be collected in an opportunistic way, as they are
found accidentally during foraging. Oii the contrary, cultivated fruits (of large size and
concentrated in predictable patchcs) probably are searched for, as suggested by the coincidence of
ripening season and occurrence in faeces, and the presence of soil within faeces, explained by an
undertree foraging behaviour. However, animal food is likely to be necessary even in small
quantities, compensating for the lack of protein in a vegetarian diet (Campalini & Lovari, 1985),
To conclude, irrigated cultures may be a condition for badger presence in arid regions.
Agricultural practice has also been said to favour badgers in other areas (Neal, 1986).
We thank F. Hiraldo and F. Palorrtares for collecting material, DGTCYT (project PB87-0405) for financial
support, C. Keller for improving the English version and an anonymous referee for improving a previous
draft.
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