herp 3/19

Introduction to Animal Movement

• Importance of understanding why animals exhibit movement.

• Key Concept: Predator avoidance as a driving force in behavior strategies.

Reasons for Animal Movement

• Resource Centralization: Animals often move to areas where food is available.

• Shelter Seeking: Animals may seek shelter when environmental conditions are harsh or stressful.

• Reproduction: Movement to find mates is a significant motivator.

  • Hunting for mates can be seen as a resource for reproductive success.

• Resource Depletion: Animals might deplete resources in one area and must move to find better patches.

  • Concept of optimal foraging theory comes into play, where animals seek out areas with the best resources.

• Predation Risk: Movement can also be influenced by the need to avoid predators.

• Risk and Reward: Overall, two categories can summarize the reasons: risk (physiological stress, predation) and reward (food, mates, shelter).

Key Terms

• Home Range:

  • Defined as the area an individual regularly moves within, not defended from others.

  • Associated with one or more types of resources.

  • Can vary by species, sex, body size, life stage, and population density.

  • Example: Larger individuals often have larger home ranges.

Estimating Home Ranges

• Minimum Polygons:

  • Method to estimate home range using observed points to create a polygon outlining activity area.

• Probabilistic Fixed Kernel Estimates:

  • A more sophisticated method that uses data density to find the most common areas of activity, reducing the impact of outliers.

• Examples of home ranges:

  • Variations in home range sizes based on species, such as the blue iguana exhibiting different home ranges by sex.

Three-Dimensional Home Ranges

• Certain species utilize three-dimensional space (e.g., sea turtles diving).

• Challenges exist in measuring available space for animals that need specific habitats (like tree frogs needing branches).

Small Home Ranges

• Some amphibians, like mole salamanders, have tiny home ranges due to their underground habits.

• Migrations for breeding are often not included in home range calculations due to being considered separate.

Species Examples:

• Crawfish Frogs: Exhibit small home ranges due to their burrow fidelity and behavior against predation.

• Habitat shapes can impact home range morphology, with river-dwelling animals having more linear patterns.

  • Example of soft-shell turtles adapting to dynamic river systems and food availability affecting movement.

Seasonal Movements and Breeding

• Changes in home ranges occur based on breeding behaviors, food availability, and environmental conditions.

• Example of Scaloporus species showing male home ranges expand during breeding seasons.

Territoriality vs Home Range

• Territories: Defined sections of a home range actively defended against intruders, often by males to secure resources for reproductive success.

• Risks involved in maintaining territories include increased exposure to predators and potential injury from conflicts with other individuals.

• Behaviors such as vocalizations and push-up displays are common in territorial mammals and reptiles.

Territoriality in Reptiles and Amphibians

• Trade-offs play a role in territorial behaviors, with testosterone levels often influencing aggression and territoriality among males.

• Examples: Satellite behavior in tree frogs and contests among bullfrogs for oviposition sites.

Non-territorial Behaviors

• Some species like snakes are generally non-territorial, while lizards are more likely to defend territories related to food availability.

Conclusion

• Variation exists in territorial defense strategies among species, influenced by resource availability, population density, and physiological needs.

• The relationship between home range and territory is complex and varies widely amongst different species.