Habitat Use and Diet
Introduction to Habitat Use and Diet
Understanding habitat use and diet is crucial in wildlife ecology.
It informs management decisions regarding vegetation manipulation to support or penalize different species.
Required reading: Chapter 7 of Bollin and Robinson and the relevant techniques manual.
Habitat Use and Selection
Habitat use and diet are interconnected concepts.
Both involve organisms selecting from available resources, either consciously or subconsciously.
Survival and reproduction influence these choices.
Habitat Definition:
Habitat is the set of resources and conditions that allow occupancy and reproduction of a species.
It is species-specific; thus, there is no universal term like "good wildlife habitat."
Common misconceptions include using "habitat" interchangeably with "vegetation" or "cover type."
Misused Terms in Habitat Ecology
Habitat Abundance vs. Availability
Habitat abundance considers what humans perceive as available to wildlife, while availability is the actual amount present.
Example: Snowshoe hare habitat must be understood from the hare's perspective.
Habitat Quality:
Reflects an environment's ability to support population persistence.
Determined by reproductive success and survival rates specific to a species.
Habitat Type:
Often misused to refer to vegetation; should specify vegetation type instead.
Key Concepts in Habitat Selection
Habitat Use:
Represents observed presence with specific cover types or food sources.
Habitat Selection:
Implies choosing particular habitats or food sources among available options.
Preferences can be evaluated independently of availability.
Hierarchical Process:
Habitat selection occurs at multiple spatial scales—from biogeographic regions to specific patches.
Example: Migrating species choose routes and specific local habitats within those routes.
Selection Orders as Defined by Johnson (1980)
First Order Selection: Overall range of a species.
Second Order Selection: Specific use of habitat types within the overall range.
Third Order Selection: Use of particular patches within habitat types.
Fourth Order Selection: Use of specific features within patches.
Examples of Habitat Use
Waterfowl Example:
Different species of waterfowl select specific wetland types (e.g., geese, swans, ducks) based on their needs (e.g., food, nesting).
Selection is not uniform across all species, highlighting individual habitat preferences.
Long-tailed Bats Study:
Analysis of habitat selection based on composition within their home ranges led to identifying areas preferentially used versus avoided.
Measurements of Habitat Use
Direct Observation: Watching animals in their environment (e.g., watching ducks in a pond).
Capture Techniques: Using traps or telemetry to assess habitat use.
Radio telemetry helps track wildlife movements and home range sizes.
Indirect Methods: Assessing signs of wildlife presence (e.g., tracks, feces, gnaw marks).
Boundaries of home ranges must reflect the biology of the study species.
Food Use and Selection
Similar principles as habitat selection apply to food preferences.
Food use can be assessed through:
Bite Counts: Tracking what animals eat.
Stomach Content Analysis: Analyzing dropped pellets or remains.
Frequency of occurrence and biomass need to be considered for accurate food use assessments.
Implications of Habitat Alteration
Changes in habitat quality and type can affect species' behaviors and population dynamics.
For example, different cutting patterns during forestry can significantly impact wildlife populations depending on species' habitat requirements.
Edge Effects:
Understanding how habitat edges change due to cutting is essential since some species thrive in edge habitats, while others may avoid them.
Conclusion
Understanding habitat use and diet is critical for effective wildlife management.
Data analysis on habitat selection reveals important ecological insights.
Future assignments will help in evaluating wildlife habitat selection in an applied context.