HORMONE CONCENTRATIONS, VAGINAL CYTOLOGY AND DIET: VARIATIONS DURING REPRODUCTION IN SEBA’S SHORT-TAILED FRUIT BAT
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Many factors influence the reproduction and fitness of organisms but lack extensive research. Reproductive endocrinology influences the estrous cycle of mammals, and consequently, their ability to bear and rear young. Moreover, dietary decisions made to satisfy nutritional requirements during pregnancy and lactation can impact development of offspring. Female physiological or dietary strategies, if compromised, may lead to unsuccessful reproduction. Due to cost and difficulties obtaining and preserving biological samples, reproductive endocrinology remains poorly studied in most free-ranging organisms. This study is one of the first to examine differences in fecal hormone (progesterone and estrogen) metabolites at different reproductive stages and in particular to determine the probability that a female bat (Seba’s short-tailed fruit bat, Carollia perspicillata) is in putative metestrus or pregnancy by correlating vaginal cytology with hormone metabolites. Fifty-five females collected throughout the reproductive season were examined for the presence of a conceptus. Furthermore, populations of cells (superficial, intermediate, and parabasal cells) in exfoliate vaginal cytology were quantified for each individual. Progesterone and estrogen concentrations increased from estrus through early pregnancy and then decreased into late pregnancy. From late pregnancy to early lactation progesterone levels continued to decrease, whereas estrogen levels increased. A logistic regression indicated that progesterone and estrogen concentrations and parabasal cell proportions were not significant predictors of whether a female was pregnant or in putative metestrus. Superficial cell proportions were highest during putative metestrus and were an effective predictor of this phase of the reproductive cycle. Reproductive status can influence dietary choices and foraging behavior. Generally, pregnancy and lactation are energetically expensive. Whereas energy availability may be one of the main precursors to reproductive success, nutrients such as calcium and nitrogen can also limit reproduction. Since energy and nutrient costs are high during reproduction, foraging strategies or choices of particular dietary items may be critical for survival of both mother and offspring. The goal of this study was to analyze dietary variation and consumption of nitrogen-rich and calcium-rich items during different reproductive stages in Seba’s short-tailed fruit bat (Carollia perspicillata). Dietary analysis was done on fecal samples from males, non-pregnant, pregnant, and lactating females at the Macaregua Cave in Santander (Colombia). Diets were similar among males, non-pregnant, and pregnant females, but lactating females had the most distinct diet. All groups were general in their diets, eating a wide variety of items. Nitrogen-rich items, such as Piper and insects, were not prevalent within the diet of pregnant bats, while Piper aduncum exceeded expected frequencies in the diets of lactating bats. Pregnant females may not be nitrogen limited and may be able to satisfy the requirement with fruits that are low in protein. Lactating females may have a more difficult time fulfilling the nitrogen requirement and must consume Piper. Calcium-rich Ficus was not common or found in the diets of lactating or pregnant bats, therefore, calcium requirements must have been satisfied through other avenues.