Individual responses to habitat heterogeneity: consequences for spatial poplualtion dynamics and landscape management

A project undertaken at The Fenner School of Environment & Society, Australian National University, and supervised by Dr Sam Banks

Long-term wildlife population research provides a unique and important opportunity to identify evolutionary adaptations to, and ecological effects of, environmental heterogeneity. We are using a long-term study of bobucks (mountain brushtail possums) in tall mountain ash forests to find out how animal life histories are flexible in response to environmental variation. Changes in the availability of resources such as food or dens across the landscape and through time can affect the survival and reproductive output of individuals. We are looking for evidence of resource limitation associated with environmental heterogeneity by studying spatial and temporal variation in growth, survival and reproductive output of bobucks in a population at Cambarville in the Victorian Central Highlands. We predict that flexibility of life history strategies might enable individuals to maximise their fitness in response to environmental heterogeneity and/or resource limitation. For instance, we have found that smaller female bobucks, and those that live in cool-temperate rainforest zones within the mountain ash forests, are more likely to produce male offspring. Males are the dispersing sex, so these females are less likely to suffer from resource competition from their young. We are using long-term mark-recapture records, genetic, physiological and parasitological data to identify behavioural and physiological strategies that animals use to respond to environmental heterogeneity. In addition to offspring sex allocation, these responses might include dispersal behaviour, social interactions and mating systems, or habitat use patterns.

The work is interesting from an evolutionary ecological perspective, but also has broader relevance to population dynamics and conservation. How animal populations respond to environmental variation is a major question in population biology and conservation management. To a large extent, spatial or temporal changes in animal populations are the result of processes that act at the level of the individual, such as reproductive output and survival. Therefore, the individual-level life history responses that we document may have consequences for population dynamics on a larger scale. We expect that an improved understanding of how individuals and populations respond to natural and human-induced variation in will improve our ability to integrate wildlife conservation in multiple use landscapes with other activities such as forestry.

 
Figure 1.Victorian Central Highlands mountain ash forest.

Figure 2. Cool-temperate rainforest understorey.

Figure 3. Victorian Central Highlands mountain ash forest.

 

Figure 4. Lachie McBurnie collecting morphometric data.

 

Figure 5. Sam Banks releasing a mountain brushtail possum.

 

Figure 6. Mountain brushtail  possum in habitat burnt by the February 2009 Victorian fires.

 

Figure 7. Early regrowth after the February 2009 Victorian fires.

 

Figure 8. Fern regrowth in April 2009.

 

Figure 9. Many rainforest gullies escaped the February 2009 fires.