Methods of evaluating the spermatogenic ability of male raccoons (Procyon lotor)

Abstract

Feral raccoons (Procyon lotor) have been growing in number in Japan, and they are becoming a problematic invasive species. Consequently, they are commonly captured and killed in pest control programs. For effective population control of feral raccoons, it is necessary to understand their reproductive physiology and ecology. Although the reproductive traits of female raccoons are well known, those of the males are not well understood because specialized knowledge and facilities are required to study them. In this study, we first used a simple evaluation method to assess spermatogenesis and presence of spermatozoa in the tail of the epididymis of feral male raccoons by histologically examining the testis and epididymis. We then evaluated the possibility of using 7 variables—body weight, body length, body mass index, testicular weight, epididymal weight, testicular size and gonadosomatic index (GSI)—to estimate spermatogenesis and presence of spermatozoa in the tail of the epididymis. GSI and body weight were chosen as criteria for spermatogenesis, and GSI was chosen as the criterion for presence of spermatozoa in the tail of the epididymis. Because GSI is calculated from body weight and testicular weight, this model should be able to be used to estimate the reproductive state of male raccoons regardless of season and age when just these two parameters are known. In this study, GSI was demonstrated to be an index of reproductive state in male raccoons. To our knowledge, this is the first report of such a use for GSI in a member of the Carnivora.

Morphological reproductive characteristics of testes and fertilization capacity of cryopreserved sperm after the Fukushima accident in raccoon (Procyon lotor)

“…A few studies have attempted to elucidate the effects of physiological and ecological factors on raccoon reproductive activity, including litter size, pregnancy rate and reproductive season (Asano et al., 2003; Sanderson & Nalbandov, 1973). Indeed, the influence of seasons on raccoon testicular function and spermatogenesis has been recently reported (Kaneko et al., 2005; Okuyama et al., 2014; Uno et al., 2014). In this study, the seasonal reproductive cycle stages were classified as either reproductive or non‐reproductive.…”

Seasonal changes of the prostate gland in the raccoon (<i>Procyon lotor</i>) inhabiting Hokkaido, Japan

“…Male raccoons show a decrease in testicular function and sperm number in the epididymis between June and September [53]. In the raccoons in Japan, the absence of sperm in the epididymis due to reduced spermatogenesis in the testes was observed from July to October in Kanagawa [28,61] and from July to September in Hokkaido [44]. However, this reproductive characteristic is not synchronized in all individuals of the same regional population.…”