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

INTR. MAT&MET. RESUL. DISCU.

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)

INTR. MAT&MET. RESUL. DISCU.

M. Tschapka

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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M. Tschapka D. Villalobos

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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