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A cruising forager. JCM |
Foraging
behavior in lizards has been classically described as either active foraging or
ambush (also called sit-and-wait). Both types of foraging behavior have been
correlated with morphological, behavioral, and habitat traits. Active foragers,
for example, have higher activity levels, caloric intake, and body temperatures
compared with ambush foragers. However,
chameleons have unusual morphological and behavioral traits that undoubtedly
influence feeding behavior. The moniker, “cruise forager,” was first suggested
by Regal (1978) as an intermediate stage between active and ambush foraging. Regal
(1983), later defined cruise foraging as
an animal that moves, stops, scans the environment, then moves, stops, and
scans again. Observing the chameleon Bradypodion
pumilum foraging for food prompted Butler (2005), to propose chameleons compose
a third foraging class, the “cruise foragers.”
Hagey et al. (2010) observed Jackson’s chameleon, Chameleo jacksonii xantholophus on the island of Hawai’i. The
species is endemic to Mt. Kenya, Kenya, but was introduced to Hawai’i in the early
1970’s and has spread to several other islands in the Sandwich group. The
lizards were filmed, measured, and their microhabitat described. The video was
used to quantify the lizards’ foraging behavior and it was compared to the
behavior reported by Butler (2005). The results suggested that Jackson’s
Chameleon exhibits a moderate percent time moving (19.7%), has a low number of moves
per minute (the mean was 0.24); and a very slow locomotion speed. This
combination is rarely seen in other lizard species, but it is strikingly
similar to data from the only other chameleon studied, B. pumilum. The authors suggest that another lizard, other than other
true chameleons (family Chamaeleonidae), that may be a cruise forager is the
polychrotid, Chamaeleolis, which is
in a different lineage than the true chameleons – it is closely related to the
anoles. As for “cruise foraging” as a new class of hunting behavior in lizards,
these authors agree that it should be recognized.
Literature
Butler, M. A.
2005. Foraging mode of the chameleon, Bradupodion
pumilum: A challenge to the sit-and wait versus active forager paradigm? Biological Journal of Linnean Society, 84:797–808.
Hagey, T. J., J.
B. Losos, and L. J. Harmon. 2010. Cruise
Foraging of Invasive Chameleon (Chamaeleo
jacksonii xantholophus) In Hawai'i. Breviora
519:1-7.
Regal, P. J.
1978. Behavioral differences between reptiles and mammals: An analysis of
activity and mental capabilities, pp. 183–202, In N. Greenberg, and P. D.
MacLean (eds.), Behavior and Neurology of
Lizards. Rockville, Maryland, National Institute of Mental Health.
Regal, P. J.
1983. The adaptive zone and behavior of lizards, pp. 105–118. In R. B. Huey, E.
R. Pianka, and T. W. Schoener (eds.), Lizard
Ecology: Studies of a Model Organism. Cambridge, Massachusetts, Harvard University
Press.
Labels: chameleons, cruise foraging, foraging behavior, lizards