Herpetology Foraging (10)

Instructor: Dr. Jason R. Bohenek
Lecture: MWF 11-11:50
Lab: W 1-3:50pm
MS Teams: @Bohenek, Jason

Behavioral Ecology: Foraging

Objectives

• Understand the diverse diets of herpetofauna (herps) including variations across species and environments.

• Learn the mechanisms by which herps detect and capture their prey, analyzing both sensory modalities and behavioral strategies.

Overview of Herpetofauna Diets

The basic rule in herpetology is that herps will consume anything that fits into their mouth, reflecting the opportunistic feeding strategies many species adopt. Herpetofauna include amphibians and reptiles, which are integral to their ecosystems as they manage prey populations and serve as prey themselves in food webs. Their diets can be broadly categorized as follows:

• Caecilians: Primarily consume earthworms and various invertebrates, utilizing burrowing tactics to access soil-dwelling prey.

• Frogs & Salamanders: Adult forms typically feed on insects, with some species showing preferences for specific types of prey, such as beetles or ants, due to their hunting strategies.

• Crocodylians: These opportunistic feeders primarily target other vertebrates, employing ambush predation techniques.

• Turtles: Exhibit a mixed diet consisting of both aquatic plants and small animals, which variably shifts with seasonality and habitat availability.

• Squamates (lizards and snakes): Diets range from invertebrates to other vertebrates, with groups like the Iguanidae and Leiolepidinae displaying herbivorous tendencies, resulting in adaptations for plant consumption.

Foraging Modes

Sit-and-wait (Ambush)

• This strategy involves minimal searching, focusing more on energy-efficient methods of capturing prey once it comes within reach.

• Predators employing this mode often utilize environmental features, such as rocks or vegetation, to conceal themselves while relying on visual or thermal cues to respond to prey movements.

Active Foraging

• Active foragers invest considerable energy in locating prey, often traversing large areas and using visual and chemical cues.

• They exhibit a diverse range of hunting behaviors, including stalking and chasing, adapting their strategies based on the type of prey and environmental conditions.

Foraging Behavior Evolution

• Herps showcase behavioral plasticity, adjusting their foraging behaviors in response to temporal variations in prey abundance and availability.

• The Optimal Foraging Theory suggests natural selection favors individuals that maximize energy intake while minimizing energy expenditure, particularly evident during periods of food scarcity, which can lead to a broader range of prey selection.

Detecting, Capturing, and Eating Prey

Prey Detection Mechanisms

• Visual Cues: Herps are adept at detecting moving prey through visual recognition systems that are highly tuned to stimuli in their environments.

• Chemical Cues: Essential for locating non-moving prey, many herps, particularly snakes, rely heavily on their vomeronasal organ to process scents in their surroundings.

• Tactile & Thermal Cues: Both moving and stationary prey can be detected through specialized sensory adaptations. For example, certain snakes can sense temperature variations which indicate the presence of warm-blooded prey.

• The specific modalities employed can vary significantly among different herpetofauna groups, shaping their ecological niches.

Visual Detection in Frogs

• Research has identified four critical aspects of visual recognition in frogs, particularly in relation to neurophysiological studies: detection of sharp edges, movement tracking, response to dimming images indicating potential predators or prey, and the ability to recognize curvature of objects in their field of view.

• Frogs possess 360° ground-level vision, which helps them focus on immediate stimuli while maintaining awareness of their surroundings.

• Their multifocal lenses enhance visual acuity under various light conditions, contributing to hunting success in differing environments.

Pupils and Vision Optimization

• Slit-shaped pupils enable frogs to utilize their lenses fully in rapidly changing light conditions, optimizing their visual capabilities and thereby enhancing prey capture efficiency. This anatomical adaptation is crucial for survival in diverse habitats where light intensity can vary dramatically.