Proceedings of the Seventh Mountain Lion Workshop

FACTORS AFFECTING DISPERSAL IN YOUNG MALE PUMAS
JOHN W. LAUNDRÉ, Instituto de Ecologia, A.C, Km 5 a Carr. de Mazatlán s/n, C.P 34100,
Durango, Dgo México, email: launjohn@prodigy.net.mx
LUCINA HERNÁNDEZ, Instituto de Ecologia, A.C, Km 5 a Carr. de Mazatlán s/n, C.P 34100,
Durango, Dgo México, email: lucina@fauna.edu.mx
Abstract: Numerous studies have demonstrated that nearly all young male pumas disperse from their natal home
range area while most females are philopatric. There are 2 hypotheses for the driving force behind dispersal in
young male pumas. The first is the competition (aggression avoidance) model where dispersal is because of
competition between young males and their fathers/incoming transient males for mates and resources. The second is
the inbreeding model where young males are thought to disperse to avoid inbreeding with their mothers/sisters.
Under each model, specific predictions can be made to test their validity. Under the competition model, we predict
that there should be physical conflicts between sons and their fathers, including infanticide and that competitive
ability should increase with age and thus, the longer time and further distance they are from their home area. Thus,
dispersal distances should reflect their competitive ability, i.e. few males will establish territories close to their natal
home range. Under the inbreeding avoidance model, we predict fewer physical conflicts (young males leave on
their own), no inbreeding between fathers and daughters, which is genetically equivalent to sons mating with their
mothers, and no males should establish their territories adjacent (1-2 home range diameters) to their natal home
range. We tested these predictions with dispersal data from our study in southern Idaho/northwestern Utah and
published data. We refuted the inbreeding model because resident males do fight and kill their male offspring,
resident males do mate with their daughters, and there is a high percent of males that establish their territories within
2-4 HRDs of their natal home ranges. Our data supported the competition model with an increase in frequency of
dispersal distances at >2 diameters. We conclude that young males are forced out of their natal home range by their
fathers or incoming males who, by default, will be older and stronger. We propose that they continue to disperse
until they gain enough weight and experience to successfully takeover a territory.
Key Words: male pumas, dispersal, inbreeding, competition, Idaho, Utah
Numerous studies have demonstrated
that nearly all young male pumas disperse
from their home range area while most
females are philopatric (Ross and
Jalkotzy1992, Sweanor et al. 2000). There
are 2 hypotheses for the driving force behind
dispersal in young male pumas that have
been developed considering the various
costs and benefits to dispersing vs
philopatric behaviors (Shields 1987). The
first is the competition model where
dispersal is motivated by interference
competition and aggression between young
males and their fathers/incoming transient
males for mates and resources (Dobson
1982, Moore and Ali 1984). The second is
the inbreeding model where young males are
thought to disperse to avoid inbreeding
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Proceedings of the Seventh Mountain Lion Workshop
primarily with their mothers/sisters (Wolfe
1994). There have been extensive reviews
and criticisms of both hypotheses and it
continues to be a hotly debated topic (See
Shields 1987 for a review). Relative to
pumas, discussions of dispersal have
primarily centered around dispersal ages and
distances but little on the driving force
behind dispersal, especially for young
males. Sweanor (1990) reported on
dispersal in male pumas in New Mexico and
concluded that the likely driving force was
competition among males. However, later,
Logan and Sweanor (2001) concluded that
male pumas were dispersing primarily to
avoid inbreeding. Thus at this time it is
uncertain which hypothesis might best
explain dispersal in young male pumas.