Ds. Jacobs, The diet of the insectivorous Hawaiian hoary bat (Lasiurus cinereus semotus) in an open and a cluttered habitat, CAN J ZOOL, 77(10), 1999, pp. 1603-1608
Citations number
26
Categorie Soggetti
Animal Sciences
Journal title
CANADIAN JOURNAL OF ZOOLOGY-REVUE CANADIENNE DE ZOOLOGIE
The Hawaiian hoary bat, Lasiurus cinereus semotus, foraged in both an open
and a cluttered habitat. In the cluttered habitat it used slow, manoeuvring
flight. In the open habitat it used rapid, less manoeuvring flight with ec
holocation calls of higher frequency than in the cluttered habitat. The com
bination of faster flight with higher frequency echolocation calls means th
at it should detect insect prey too late to manoeuvre for capture unless it
preyed on relatively larger insects in the open habitat. The mean size of
dietary items should therefore be greater in the open habitat than in the c
luttered habitat. There should also be a greater preponderance of larger in
sects in the open than in the cluttered habitat to ensure that the use of r
apid flight with higher frequency echolocation calls is efficient. I tested
these predictions by comparing the diets and insect fauna in one open site
with those in one closed site on the island of Hawai'i. As predicted, the
dietary items were larger (t = 60.9, df = 259, p < 0.00001) in the open hab
itat (length = 18.9 +/- 1.3 mm (mean +/- SD); range 14-24 mm) than in the c
luttered habitat (6.5 +/- 1.6 mm; range 4-15 mm). In the cluttered habitat
86% of the insects fell into the three smallest length categories, while 52
% of the insects in the open habitat fell into the two largest length categ
ories. The preponderance of larger insects in the open habitat, with the co
nsequent increase in detection range, enabled the bats to increase their fl
ight speed despite their use of higher frequency echolocation calls. Rapid
flight increases the rate at which insect prey are encountered and improves
the foraging efficiency of bats. This provides evidence that bats are capa
ble of altering their foraging strategy in response to prey characteristics
and not just to the physical environment.