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Characteristics of estrus, mating, and pregnancy were studied in captive fennec foxes. The monestrous cycles had mean intervals of 9.9 (+/- 1.2) months, whether or not pups survived to weaning. Proestrus, judged by vulval swelling, began 6.5 (+/- 0.7) days before estrus and was not accompanied by sanguineous discharge. Percentage cornified epithelial cells in vaginal smears increased at the time of estrus. In 8 of 10 estrous periods, a single mating followed by an extremely long copulatory lock (mean 1 h 58 min) was observed during continuous video monitoring. In the other two cycles, copulation occurred 2 and 3 times. Patterns of both fecal and serum estradiol and progesterone concentrations during estrous cycles were similar to those reported for other canids.
Key words: canid, fennec fox, gestation, mating, ovulation, reproduction, Vulpes zerda
Monestrous cycles, rare among mammals, are characterized by a single ovulatory period followed by pregnancy (if fertilization occurs) or by a prolonged diestrous phase (if nonfertile), then anestrus (Asa 1996; Conaway 1971). Monestrum has been most often described for temperate-zone canid species that have only one estrous period during a restricted breeding season. However, monestrum does not define the number of estrous periods per year but describes the sequence of estrous cycle phases, that is, in a nonfertile cycle, monestrum comprises proestrus, estrus, diestrus, and anestrus, whereas polyestrum, in contrast, comprises proestrus, estrus, and diestrus followed immediately by proestrus without an intervening period of anestrus. Both monestrum and polyestrum can be either seasonal or continuous.
All canid species studied to date are reported to be monestrous (Asa 1997, 1998; Asa and Valdespino 1998), and most have only 1 seasonal cycle per year; anestrus accounts for the remainder of the annual cycle. However, the vast majority of data are for temperate- and arctic-zone species, e.g., gray wolf (Canis lupus), coyote (C. latrans), red fox (Vulpes vulpes), and arctic fox (Alopex lagopus-for review see Asa and Valdespino, in press). Little is known about tropical zone canids that, without the seasonal constraints faced by species at higher latitudes, might have nonseasonal, monestrous cycles like the domestic dog (mean cycle length approximately 8 months-Christie and Bell 1971). In fact, the South American crab-eating fox, Cerdocyon thous (Brady 1978) and bush dog Speothos venaticus (Porton et al....