Effects of conspecific behavior and refuge complexity on anti-predator decision making

Author: Elizabeth TranMentor: Dr. Esteban Fernández-JuricicAffiliation: CSULB

Outline

Introduction Materials and methods Expected results Conclusion Future experiments

Introduction House Finch (Carpodacus mexicanus)

Introduction Geographic range

Abundant bird often associated closely with human habitation.

Habitat Native western population occurs in a wide variety of

habitats ranging from undisturbed desert to chaparral and open coniferous forests to cities

Prefers edge habitat, and even in desert areas, these finches require a source of water, as well as structures for perching and nesting

Introduction

Why House Finches? Abundance Easy to handle Good model for predator-

prey interaction

Why a raptor? Good predator in the wild A convincing predator Natural predator of

House Finches along with cats and snakes

Introduction Current Understanding

Studies of lizards Thermal Cost Reaction to predator Repeated attacks Tradeoffs

Reaction of bird to Predator Before and after response

No studies have been performed that show prey reaction of birds in a refuge after an attack

Introduction What will I do?

Determine the scanning (duration and rate) intake rate feeding time handling time foraging efficiency recovery time searching time (duration and rate) time in refuge (3 levels) time in link moving rate in link moving rate in refuge

Hypothesis Focal animal with conspecific foraging will also

forage without scanning Flock with animal foraging will perceive that there is no predator

Focal animal with conspecific scanning will also scan while foraging

Scanning means that there are predators nearby

Focal animal in refuge with low foliage will return to foraging faster

Not enough cover has higher cost than staying in refuge

Introduction

Materials and methods Animal collection/sample size

House Finches will be caught by OCVC staff under its license

90 adult individuals from local populations (similar proportion of males and females)

Materials and methods Animal care

Feeding (water and sunflower seeds with variety of other seeds)

Placed in Animal Facilities with constant air temperature

Infection control Removal of bedding daily Animal that contain certain disease (West Nile

Virus) will be remove from the population

Materials and methods Treatments and general procedures

All House Finches are tagged Animals will be housed in groups and will

undergo the experimental conditions only once Experiment will be conducted during the non-

breeding season Food deprivation period

Materials and methods

Focal individual

1 2

1, 2 = peripheral enclosures

Refuge

Materials and methods 2 manipulations

Conspecific behaviors 3 levels

control with no conspecifics, conspecifics foraging, conspecifics scanning

Foliage 2 levels

low high

Materials and methods Statistical analyses

Statistica Software

Factorial ANCOVA

To determine if there is a significant difference in refuge usage in each manipulation (social condition, cage condition, etc.)

Determine the recovery time for each manipulation

Expected results

Table 1. Variables recorded from each experiment. (Similar table to Creswell, Quinn, Whittingham, & Butler, 2003)(Standard variables are in bold and were in all initial models.)

type of variable variable

individual birds Individualsexbody condition (mass/wing length)

confounding variables trial numbera

days in captivitya

model flight speedtime of experimentfeeding time (hunger level)position of the House Finches in the experimental cage

vigilance variable head-up rateb

mean duration of head-up periodsb

proportion of time spent with head upb

scanning time

foraging variable mean duration of head-down (food searching) periodb

peck rateb

handling timeintake rateforaging efficiencyfeeding time

response variable time from first possible appearance of the model to response (transformed by log)response type (flight or freezing)recovering time

refuge variable time in refuge in three levels (low, middle, high)time in the linkmoving rate-linkmoving rate-refuge

Expected results

Figure 2. The speed of House Finches response to an approaching model sparrow hawk was dependent on the head-up rate. The graph illustrates residual transformed response time (controlling for position of the House Finches, model speed, trial number and body condition) with head-up rate. (Similar graph to Creswell, Quinn, Whittingham, & Butler, 2003)

Expected results

Figure 3. Head-up rate was dependent on the peck rate. Non-significant variables removed from the model were, sex, response type, trial number and body condition. (Similar graph to Creswell, Quinn, Whittingham, & Butler, 2003)

Expected results

Time spent in refuge

Refuge patch foliage

Low

High

Figure 4. The time House Finches spend in the refuge corresponded to the amount of foliage of the refuge depending on the attack condition of the predator and trade-off.

Conclusion

The predation risk forces the animals to use anti-predator behaviors having increased associated cost Increasing time spent in

the refuge Increase time spent

scanning

The emergence from refuge increases when the amount of food availability was high and when the predator’s attack was unsuccessful

Future experiment

Understand mechanism where focal animal make use of refuge and patch exploitation

Acknowledgements

Dr. Esteban Fernández-Juricic Dr. Robert Cummings (Orange County

Vector Control )

Dr. Mason Howard Huges Medical Institute Nima Gilak