Socialization/Introduction of Giant Pandas That Exhibit Inappropriate Adult Inter-Sexual Behavior
One of the primary reasons cited for captive giant panda reproductive failure was that very few males were breeding, because they reacted hyperaggressively to potential mates. Cases in which giant pandas have displayed hyper-aggressive behavior toward potential mates typically occurred between unfamiliar individuals that were not given the opportunity to engage in chemical communication before the introduction. Studies focusing on mammal species displaying breeding reticence in captivity have found that a gradual process of controlled exposure that allows individuals to become familiar with each other before a breeding introduction reduces aggression and increases courtship behavior. In this study we used a step-wise process to familiarize adults before breeding introductions to reduce aggression and increase courtship behavior.
Through our study of adult reproductive behavior, we identified three individuals (2 males, 1 female) at the Chengdu Research Base with histories of unsuccessful breeding introductions. All three subjects had reacted to potential mates with high levels of aggression during breeding introductions, and both males had injured females in breeding introductions.
The completion of a new holding facility at the Chengdu Research Base in 2001 (funded with loan money from Zoo Atlanta) allowed individuals in this study to have more exposure to potential mates than in previous years. This was consistent with our recommendations based on findings from our research. Specifically, two adult males that were isolated from females in 1999 and 2000 were housed adjacent to females for part of the 2001 breeding season. Comparisons of male behavior in the 1999 and 2001 breeding seasons revealed that most of the behaviors associated with sexual interest and chemical communication (e.g., urine mark, olfactory investigation, and body rub) increased for both males when they were housed adjacent to adult females.
One of these males was given access to an experienced estrous female in 2002 and successfully copulated. He has copulated with multiple females each year since then. The other male was given access to an experienced estrous female in 2004 and successfully copulated. Unfortunately the female included in this study never displayed sufficient interest in a potential mate to be given access for breeding. She is now 21 years old and may have reached reproductive senescence. She did not exhibit estrous behavior in 2003 or 2004. She was artificially inseminated, but did not give birth.
Our findings indicate that males with previous histories of unsuccessful breeding introductions can be successfully socialized with a gradual introduction process using step-wise desensitization and familiarization. Based on these results we have encouraged Chengdu Research Base personnel to begin to familiarize young males entering reproductive maturity to estrous females. In 2004, a 5.5 year old male that is also a subject in the developmental study was introduced to an estrous female and copulated. We hope this is the start of a new trend, and that all young males at the Chengdu institutions can be recruited into the breeding population.