Document: ADE-3-49-5

Chance favors the prepared dung beetle.

MEGIAS, A.G.* ¹ and F.S.PINERO ²

Univ. Granada, 18071 Granada, Spain. ¹
Univ. California, Davis, Davis CA 95616, U.S.A. ²

Abstract:
Reproductive success integrates the physiological conditions of individuals and the constraints on suitable nesting requirements and resource availability for the offspring. We studied reproductive physiology and nesting of two dung beetle species, Onthophagus merdarius and Onitis ion, in an arid region of SE Spain. In this area, the harsh climate imposes a short spring breeding season. We recorded physiological (ovariole conditions, fat bodies, spermatheca content, yellow bodies, ovocite reabsorption) and morphological traits (tibial wear) related to nesting. Rates of dung desiccation and habitat selection for nesting were investigated to consider ecological constraints on reproductive success. Shortly after emergence (< 1 week) most females of both species had mature ovaries, large amounts of fat bodies and spermatheca with sperm. These conditions indicate that females are prepared to nest soon after they emerge, to cope with the short spring in this desert region. However, few females had yellow bodies at the base of the ovariole (and numbers of yellow bodies were low when they occurred) and reabsorption of ovocites was common (specially in Onitis ion) suggesting that females lay few eggs. This conclusion is supported by the observation that females rarely had extensive tibial wear characteristic of those that have dug several nests. These results indicate that the low reproductive and nesting rates are not due to physiological constrains or food limitation. Instead, we speculate that high dung dessication rates and limitation in suitable nesting habitat constrain reproduction in these desert dung beetles. Thus, in this harsh environment, females that are prepared physiologically can take advantage of nesting opportunities when they arise.

Keywords: Desert, dung beetles, nesting, reproductive physiology, Spain.

This abstract is being presented at: 3:30 PM in session:
ANIMAL ECOLOGY