Ecological interactions, social organization, and extinction risk in African wild dogs
The conservation of wild dogs depends on the persistence of small populations because African wild dog (Lycaon pictus) populations are low in density, are limited by range loss, and are often restricted to parks containing fewer than 100 adults. Although major limiting factors for wild dog populations have been identified, including interspecific competition and diseases, such factors have not been translated into extinction risk. To assess wild dog extinction risks, we used individual-based simulations constructed from data from a 6-year field study in the Selous Game Reserve, Tanzania. Our simulations predicted that extinction risk for wild dogs was extremely sensitive to competition with lions. Extinction rates (for periods as short as 20 years) rose sharply to near 1.0 when lion populations exceeded moderate densities (approximately 110-140 lions/1000 km2). This prediction is remarkably consistent with, and highlights, ecological processes that may be responsible for recent patterns of extinction among wild dog populations. Infectious diseases that kill adults, such as rabies, also reduced population persistence if they increased mortality by ≥0.3 and occurred at average intervals of ≤10 years. In contrast, diseases killing only pups, such as canine parvovirus, had weaker effects on persistence. Although persistence declined sharply for mean litter sizes ≤6, persistence was unaffected by increasing mean litter size above its normal range (i.e., 8-12 in Selous). Increasing mean pack size from typical levels reduced extinction risk, but reproductive suppression may set an upper limit on pack size. Although the risk of extinction for 20- to 100-year time frames was appreciable for many realistic ecological and demographic conditions, even low immigration rates substantially increased persistence probabilities. Active management to mitigate the effects of interspecific competition, facilitate dispersal among populations, or augment population size appears essential for wild dog conservation.
Ecological interactions, social organization, and extinction risk in African wild dogs.
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