The consequences of disrupted dispersal in fragmented red-cockaded woodpecker Picoides borealis populations
Authored by JR Walters, K Schiegg, JA Priddy
Date Published: 2002
DOI: 10.1046/j.1365-2656.2002.00637.x
Sponsors:
Swiss National Science Foundation (SNSF)
Platforms:
No platforms listed
Model Documentation:
Other Narrative
Mathematical description
Model Code URLs:
Model code not found
Abstract
1. Habitat fragmentation may adversely affect animal populations through
several mechanisms. However, little is known about how the impacts of
some of these mechanisms are manifested in altered dynamics of wild
populations.
2. We used a spatially explicit individual-based simulation model to
examine the potential effects of disrupted dispersal due to
fragmentation on the population dynamics of the endangered, co-operatively breeding, red-cockaded woodpecker Picoides borealis.
3. We simulated population dynamics as a function of population size and
spatial aggregation of territories. Dispersal success (but not mortality
or fecundity) was an emergent property of model runs. In the model all
female and some male fledglings dispersed in straight lines in random
directions, and the remaining males stayed on their natal territories as
helpers and competed for breeding vacancies in their immediate
neighbourhood.
4. Population trend was tied to the higher dispersal success of both
males and females in larger and less fragmented populations. Helpers
were more successful than dispersing males. Male breeder recruitment
depended entirely on helpers when populations were small (25 or 100
territories).
5. Declining populations were characterized by high emigration rates and
both failure and delay in female recruitment. The large numbers of
unpaired males resulted in lowered reproductive output at the population
level and in the loss of territories. Populations of 25 territories were
stable when territories were highly aggregated, despite high emigration
rates. These results closely match empirical observations.
6. A number of co-operatively breeding species are endangered. The
unusual dispersal behaviour of helpers may make such species sensitive
to habitat fragmentation but also resilient to reductions in population
size when territories are aggregated. Small populations of co-operative
breeders may have considerable conservation value as a source of genetic
diversity.
Tags
Management
Dynamics
Habitat fragmentation
Metapopulation
Long-distance dispersal
Extinction
Size
Landscapes
Demographic-models
Forest fragments