Predator-prey interactions in secondary growth forests
Calilung, Henry G.
#95 Beverly Hills Subdivision, Taytay, Rizal
Abstract
Secondary growth forests are increasingly becoming the norm in the Philippines. Extensive logging
has laid waste to most of our virgin forests. The effects of such wide-spread disturbance among
predator-prey interactions have been studied in secondary forests of Antipolo. Comparisons with
data from primary forests, yield surprising results: predator-prey interactions become more complex
with increasing disturbance but only after a critical point. Beyond this, the interactions collapse.
Figure 1. A map of the Philippines. There are fewer than
500 eagles in the wild, most of which are found in
Mindanao, the largest island in the south of the
archipelago (1).
The Philippines is an archipelago of some
1,700 islands scattered in the South Eastern
corner of the Pacific Ocean (see figure 1). It
was formed 50 million years ago and has been
shaped by frequent volcanic activity ever since.
Such a colorful history has led to the evolution
of diverse and often fascinating forms of life.
And the king of such a spectacular array of
endemic species is without doubt, the Philippine
Eagle (5).
My fascination with eagles began when I
bought my first pair of binoculars and saw my
first raptor in the hills of Antipolo....
Pithecophaga jefreyi belongs to Class
Aves. The full taxonomic classification appears
below (3):
Domain - Eukarya
Kingdom - Animalia
etcetera...
The Philippines is an archipelago of some
1,700 islands scattered in the South Eastern
corner of the Pacific Ocean (see Table 1). It
was formed 50 million years ago and has been
shaped by frequent volcanic activity ever since.
Such a colorful history has led to the evolution
of diverse and often fascinating forms of life.
And the king of such a spectacular array of
endemic species is without doubt, the Philippine
Eagle (5).
My fascination with eagles began when I
bought my first pair of binoculars and saw my
first raptor in the hills of Antipolo....
Pithecophaga jefreyi belongs to Class
Aves. The full taxonomic classification appears
below (3):
Domain - Eukarya
Kingdom - Animalia
etcetera...
YEAR
% FOREST COVER
1900
90
1970
30
2000
10
Table 1. Data showing loss of
forest cover in the Philippines.
It is projected that only 3% of
our virgin forests will remain by
year 2010 (3).
Figure 2. Population vs. time graph of the predators and prey. Note that the rise and fall of both populations
are closely linked (3).
Materials and Methods
Equipment
Collapsible rodent traps (1 ft3 Rodex-All)
Custom-made pit traps (300 ml pit, dug by
hand, holds a Cola aluminum can)
Digital caliper (Vernier 500)
Digital top-loading balance (Ohaus 750,
300g max, 0.001 g sensitivity)
Laser-tripped camera with tripod (Nikon
SLR 2000, lens Nikon Zooma 1000x)
Night-vision goggles (Ex-Marine 250,
10x30)
Chemicals
70% ethanol for preserving soft-bodied
animals
tranquilizer (Sleeper 007), delivered via
the Sleeper Gun
The bird has a length of 990 cm from beak
tip to tail, etcetera...
The Philippine Eagle is rarely seen in the
wild because there are very few individuals left.
Most sightings are of birds flying close to the
canopy in search of their favorite preymonkeys. They nest in emergent dead trees to
get a commanding view of the whole landscape.
They are rarely seen in the summits of
mountains. They prefer rather, the lower slopes
where they are sheltered from the wind...
The Philippine Eagle is rarely seen in the
wild because there are very few individuals left.
Most sightings are of birds flying close to the
canopy in search of their favorite preymonkeys. They nest in emergent dead trees to
get a commanding view of the whole landscape.
They are rarely seen in the summits of
mountains. They prefer rather, the lower slopes
where they are sheltered from the wind...
Results and Discussion
Pithecophaga jefreyi takes about 20 to 30
years to reach maturity. It lays only one egg
during the cold December month and does so
only every two years. The male and female
mate for life and are both very active in taking
care of their chick which grows at a tremendous
pace. It takes only 5 months for the chick to be
fledged but will spend a long time as a juvenile
before looking for a mate... (3)
Recent sightings of this eagle have been
limited mainly to the forests of Mindanao
though anecdotal reports indicate that the bird
once flew over most of the major islands of the
Philippines. It is found nowhere else in the
world and so it is rightfully considered as a
symbol of the Philippine’s ecological battle
with a rising tide of environmental
degradation.... (6)
Pithecophaga jefreyi takes about 20 to 30
years to reach maturity. It lays only one egg
during the cold December month and does so
only every two years. The male and female
mate for life and are both very active in taking
care of their chick which grows at a tremendous
pace. It takes only 5 months for the chick to be
fledged but will spend a long time as a juvenile
before looking for a mate... (3)
Recent sightings of this eagle have been
limited mainly to the forests of Mindanao
though anecdotal reports indicate that the bird
once flew over most of the major islands of the
Philippines. It is found nowhere else in the
world and so it is rightfully considered as a
symbol of the Philippine’s ecological battle
with a rising tide of environmental
degradation.... (6)
Recommendations
The Philippine Eagle is critically
endangered with less than 500 individuals in the
wild. The main reason for this is the destruction
of its habitat on a major scale. Illegal logging
practices in the past 50 years have reduced most
of the archipelago’s virgin forests to a mere
shadow of what they once were. In fact, it is
predicted that only 3 percent of our virgin
forests will remain by 2010...
References
(1) Agence France-Presse. RP makes
conservation history as eagle released.
Philippine Daily Inquirer. April 23,
2004.
(2) Birdlife International. Working together for
birds and people.
<http://www.birdlife.org> February 23,
2006.
(3) Godown, M., and A. T. Peterson. 2000.
Preliminary distributional analysis of
UD endangered bird species.
Biodiversity and Conservation 9:13131322.
(4) Kennedy, R. S., P. C. Gonzales, E. C.
Dickinson, H.C. Miranda, Jr., and T. H.
Fisher. A Guide to The Birds of the
Philippines. New York, United States:
Oxford University Press, Inc. 2000.
(5) Peterson, A. T. 2001. Predicting species
geographic distributions based on
ecological niche modeling. Condor
103:599-605.
(6) Sanchez-Cordero, V., V. Cirelli, M.
Munguia, S. Sarkar. 2005. Place
prioritization for biodiversity
representation using species’ ecological
niche modeling. Biodiversity
informatics 2:11-23.
Appendix
A..................... Flowchart of methods
B ..................... Photos of methods
C ..................... Journal
D..................... Raw data tables, graphs
E ..................... Maps
F ..................... Acknowledgement
APPENDIX A - Flowchart of methods
APPENDIX B - Photos of methods
Night-vision goggles
(Ex-Marine 250, 10x30)
Collapsible rodent traps (1 ft3 Rodex-All)
Digital caliper (Vernier 500)
Custom-made pit traps (300
ml pit, dug by hand, holds a
Cola aluminum can)
Laser-tripped camera with tripod (Nikon
SLR 2000, lens Nikon Zooma 1000x),
laser and tripod not shown
Digital top-loading balance (Ohaus 750,
300g max, 0.001 g sensitivity)
APPENDIX C - Journal
Day 1 - September 1, 2005
 recon of site
 noticed lots of bugs, must use insect repellant
Day 2 - September 5, 2005
 set-up pit-traps to test sampling efficiciency
Day 3 - September 6, 2005
 pit-traps highly successful
 lots of insects caught but most are hard to identify, must consult with professor in LB
ETCETERA....