Foraging Behavior of Ectophylla alba (Chiroptera: Phyllostomidae), an Extreme Food and Habitat...
Transcript of Foraging Behavior of Ectophylla alba (Chiroptera: Phyllostomidae), an Extreme Food and Habitat...
Foraging Behavior of Ectophylla alba (Chiroptera:
Phyllostomidae), an Extreme Food and Habitat Specialist
David Villalobos-Chaves*, Elisabeth. K. V. Kalko, Katrin Heer and
Bernal Rodríguez-Herrera
Universidad de Costa Rica
Programa para la Conservación de los Murciélagos de Costa Rica
• Animal activities can be influence by several factors such as body size, resource
distribution, competition, others (Morrison 1978, Kalko et al., 1999, Winkelmann et al., 2000)
• Influence of “diet amplitude” = Activity of specialized species depend strongly of
specific resources (e.g food/roost)
• Activity depends strongly on food resources (e.g Carollia castanea ̶ ̶ Thies 1998)
INTR. MAT&MET. RESUL. DISCU.
M. Tschapka D. Villalobos D. Villalobos C. castanea
Influence of spatial distribution and availability of food and roosts on the foraging
behavior of highly specialized bat species
Ectophylla alba
1. Small body size (6-9 g)
2. Endemic to Caribbean slope of Central America
3. Food specialist: Ficus colubrinae (Moraceae)
4. Many roosting requirements: e.g. Tents in few species of plants
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• Hypothesis
Given the high specialization and small body size of Ectophylla, the foraging behavior
will be strongly related to spatio-temporal distribution and availability of food/roost.
• Predictions
1. Monospecific diet and differences in spatio-temporal availability of ripe fruits
promotes high variation in home range and foraging areas of individuals.
2. Due to dependence of specific resources, spatial distribution of bat locations are
strongly related with the spatial distribution of roosts and food
3. To optimize their foraging activity, in areas with more than one tree (F. colubrinae)
with ripe fruits, bats will select trees close to day roosts and with high availability of
fruits.
INTR. MAT&MET. RESUL. DISCU.
• Lowland Rainforest of Costa Rica (Reserva
Biológica Tirimbina & Hacienda Pozo Azul )
• Radiotracking of nine bats (5 M, 4 F) for ½
night (18:00 - 00:00 h): Triangulation
• Location of fig trees and tents in and around
bats´ activity areas (GPS).
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P. Camacho
• Additionally, we recorded the availability of
ripe fruits during the sampling period of five
bats (F2, F4, F5, M3, M4)
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1. We determined the amount of trees with
ripe fruits in each bats’ activity area
2. For each ripe fruiting tree, we determined
the % of the crown with fruits
Quality categories
(4) High abundance = ≥ 75%
(3) Intermediate = 50%
(2) Low = ≤ 25%
(1) Very low abundance = ≤ 5%
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D. Villalobos
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Data Analysis
• Radiotracking data
1. Home range: MCP (Morh 1947) & a-LoCoH (Getz et al., 2007)
2. Foraging and core areas (a-LoCoH)
• Figs, tents and bat locations
1. Commuting distances between tents and figs, called “Foraging distance”
(ArcGis 10.0)
2. Spatial relationship between fig trees, tents and bat locations
(“Kcroos” from Spatstat package)
3. Selection of ripe fruiting fig trees by bats (Generalized linear models)
B
INTR. MAT&MET. RESUL. DISCU.
Prediction 1. Home range and
foraging areas highly variable
A
A. Great variation between home range
of individuals
- MCP = 10.6 - 228.6 ha
- a-LoCoH = 2.6 - 24.3 ha
- Foraging Areas = 0.9 – 7.7 ha
- Core Areas = 0.2 – 2.4 ha
B. High variation between foraging
distances
- Range: 27.3 – 1950 m
- Mean: 552 ± 463 m
• Spatial aggregation of bat locations with tents and F. colubrinae.
• Also, we found aggregation of food and roost resources (Monte Carlo Test = 0.02; from
“Kcroos” analysis)
INTR. MAT&MET. RESUL. DISCU.
Prediction 2. Strong relationship between bat locations and resources
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P. Camacho
Bat individual # of trees
F2 3
F4 3
F5 8
M3 5
M4 7
Mean ± S.D 5.2 ± 2.3
Table 1. Availability of trees with ripe fruit during
sampling period of five E. alba.
• Quality values 4-3 = High abundance of ripe fruits
• 0-500 m = Short commuting distances from tents to trees
Prediction 3. Selection of trees close
to tents/high abundance of ripe fruits
• More than one fig with ripe fruits
available for all individuals (Table 1)
• All monitored individuals selected trees
with high/intermediate abundance of
ripe fruits located close to tents (Fig. C)
; (Both predictable variables = P <0.05)
INTR. MAT&MET. RESUL. DISCU.
C
• Monospecific diet (high dependence)/spatio-
temporal patterns in fruit availability promotes:
1. Highly variation in bat’s activities (similar to
Artibeus jamaicensis ̶ Morrison 1978)
2. Larger home range size (MCP) than expected
by small body size (6-9 g; Mean = 70.4 ha)
Food generalist = 12 g Dermanura watsoni
(mean = 3.6 ha ̶ Chaverri et al. 2007)
Food specialist = 12 g Carollia castanea
(mean = 29 ha ̶ Thies 1998)
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In comparison
Artibeus jamaicensis D. Villalobos
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• Spatial aggregation between Ectophylla locations and distribution of important
resources support prediction of closely relationship due to specialism
• Aggregation between tents/fig trees can be result of:
H1. Selection of resource rich areas to inhabit
H2. Similar ecological requirements of Heliconias and F. colubrinae (e.g light, soil,
others)
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• Selection of trees with specific characteristics (fruit abundance & proximity)
suggest specializations in their foraging behavior = Optimal foraging?
• Specialization of F. colubrinae & small body size exert constrains on
foraging behavior (e.g. large foraging distances & large home range),
however observed behavior could reflect one strategy to optimize energy
intake
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We conclude that:
1. Ecological specialization of Ectophylla promotes close relationship between bat activity
and resources .
2. Monospecific diet and spatio-temporal availability of fruits promotes larger activity areas
and larger foraging distances than expected by small body size .
3. Bats probably compensate energy expenditures imposed by extreme specialization, by
selecting “high quality tress”, and possible only colonize resource rich areas (to confirm).
M. Tschapka D. Villalobos
Acknowledges
• Thank you to Tirimbina & Hacienda
Pozo Azul staff, R. Sánchez, P.
Camacho, J. D. Ramírez-Fernández, A.
Arias-Aguilar, E. Rojas, M. Gamba-
Ríos, S. P. Ripperger, E. Cordero-
Schmidt, R. K. LaVal, M. Spinola, C.
Ureña, G. Barrantes and E. J. Fuchs.
E. Rojas E. Rojas E. Rojas R. Sánchez R. Sánchez
B. Rodríguez-H
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