IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Dayan, T.; Simberloff, D.; Tchernov, E.; Yom-Tov, Y. | |
| Feline canines: community-wide character displacement among the small cats of Israel | |
| 1990 The American Naturalist (136): 39-60 | |
Each of the three sympatric, syntopic small cat species of Israel is strongly sexually dimorphic. Thus, if each sex is viewed as morphologically distinct, as a "morphospecies," there are six morphospecies potentially competing with one another. The mean canine diameters of these morphospecies are remarkably evenly spaced on a log-scaled line (i.e., the size ratios between adjacent morphospecies in a size ranking are surprisingly equal). Condylobasal lengths show no such pattern. The same three species occupy a narrow band from the Nile delta to northwestern India. The Sind is at the other end of this band from Israel, and all three species are substantially smaller there. However, the canine diameters again seem to produce equal size ratios between adjacent size-ranked morphospecies. A slightly larger cat (_Felis viverrina_) occupies the Sind but not Israel. Although we lack a wild-caught female of this species, the single male we have located from the Sind suggests that this species would, when added to the others, produce a series of eight morphospecies with equal size ratios for canine diameter. It is a tenable hypothesis that intra- and interspecific competition for food has selected for these equal canine size ratios and also for the decrease in the sizes of Sind animals relative to Israeli conspecifics. By such a hypothesis, larger teeth are used to kill larger prey, on the average. For cats, canine size is likely to be more highly correlated with prey species than is condylobasal length. However, the competitive hypothesis must be preliminary because of major empirical gaps in our knowledge of the trophic ecology of these species. The prey-size distributions are unknown, it has not been shown that larger canines correlate with larger prey, and it is not known that prey are limiting. An alternative hypothesis would entail ethological interactions mediated by canine display or use in fighting, both intra- and interspecifically. Such interactions are plausible and could well contribute to a pattern of displacement. The empirical gaps prevent a definitive choice between the hypotheses. In any event, the striking similarity of our result with that of an earlier study of mustelids suggests a common explanation. |
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