Abstract
Males will alter their mating behavior to cope with the presence of their competitors. Even exposure to odors from potential competitors can greatly increase male ejaculate expenditure in a variety of animals including insects, fishes, birds and rodents. Major efforts have been made to examine males' plastic responses to sperm competition and its fitness benefits. However, the effects of competitor absence on male's sexual motivation and behaviors remain unclear, which has been proposed to be one of the causes for the poor sexual performance of some captive mammals. This study revealed that sexual motivation can be greatly enhanced in captive male giant pandas (Ailuropoda melanoleuca) by exposure to chemosensory cues from either one or three conspecifics males. It had been shown that potential rivals' odors increased males' chemosensory investigation behavior, as well as their observing, following and sniffing behaviors towards estrous females. Behaviors changed regardless of the number of rivals (one or three). Our results demonstrate the effects of potential competition on male giant pandas' sexual motivation and behavioral coping strategy. We anticipate that our research will provide a fresh insight into the mechanisms underlying poor sexual performance in male captive mammals, and valuable information for the practical management and ex situ conservation of endangered species.
Highlights
Male-male competition for access to females plays an important role in reproductive success [1]
The presence of odor sources from stimulus male pandas led to significant increases in the time subjects in both single male (SM) and multiple males (MM) experimental groups spent in chemosensory investigation of their environment (F1,10 = 15.623, P,0.001; Figure 1a)
No significant differences were found between SM and MM males, and no differences between groups were found in the frequencies of urination (F1,10 = 1.320, P = 0.290), anogenital gland secretions (AGS) scent-marking (F1,10 = 0.511, P = 0.608), body rubbing (F1,10 = 0.717, P = 0.500), bleating (F1,10 = 0.789, P = 0.468) or foot scraping (F1,10 = 2.183, P = 0.139; Figure 1e)
Summary
Male-male competition for access to females plays an important role in reproductive success [1]. Such competition includes direct physical confrontations between individuals, as well as indirect confrontation via chemosensory and/or auditory cues. According to sexual selection theory, males can enhance their reproductive fitness in a rapidly changing environment by responding effectively to the presence and number of mating rivals [2]. Mostly on insects and small vertebrates, have shown that males alter their mating behavior in the presence of rivals [2]. Exposure to chemosensory cues from conspecific males can greatly increase male reproductive investment in insects [3,4,5], fish [6], birds [7] and rodents [8,9]. Little is known about the effects of the presence of conspecifics, or chemosensory cues from them, on behaviors of large mammals, partly because the experimental procedures involved in collecting the data are difficult
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