Another reason why interbreeding between species is limited: personality conflicts. The scientists brought wild-caught woodrats into the laboratory to test female mate preferences.
They found that Bryant's woodrat females selected either Bryant's woodrat males or desert woodrat males with equal preference. Desert woodrat females, however, almost always mated with males of their own species.
The reason? The desert woodrat females were intimidated by Bryant's woodrat males due to their larger body size and aggressive nature. In contrast, Bryant's females, themselves larger, were open to mating with the smaller, more docile desert woodrat males as well as the males of their own species.
Another factor shown to be determining the number of hybrids is that hybrid offspring do not survive to adulthood as well as do the other two species. Higher proportions of Bryant's woodrats survived to their first year of adulthood than did the hybrids (33 percent vs. 10 percent). The same was the case for the desert woodrats (22 percent vs.10 percent percent). Once the hybrids reached their first year of adulthood, however, they fared as well as the purebreds.
The reason for the low juvenile hybrid survivability, the authors say, may lie in the lack of aggressiveness and ability to compete with purebred males for denning sites and in winning territorial battles. This may necessitate greater dispersal for the male hybrids pushing them out of range of female hybrids and exposing them to greater predation pressure.
Shurtliff said, "These studies offer further insight into the behavioral and ecological dynamics of hybrid zones.
Understanding these unique areas is important because there are many examples of naturally occurring hybrid zones, and new hybrid zones will form in the future as climate change and human impacts cause species distributions to shift and come into contact. For example, scientists have documented hybri
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Wildlife Conservation Society