III  Reproduction

Chapter Summary

 

Reproductive Patterns

Cotton-top tamarins have a high capacity for rapid reproduction in captivity. There have been extensive studies of female reproductive physiology but very little is known about male reproductive physiology. Females generally give birth to twins (80%), although singletons are also frequent (18%, Snowdon et al, 1985).

Occasionally, cotton-top tamarins give birth to triplets (2%, Snowdon et al., 1985), but they rarely raise all three offspring without human intervention. The gestation length for this species is 183.7 ± 1.14 days (Ziegler et al., 1987a). The first postpartum ovulation occurs within 27.3 ± 0.51 days for females that give birth to twins, and 16.0 ± 0.75 days for females that give birth to singletons (Ziegler, 1987a). Unlike many other primates, the postpartum ovulation can, and often does yield a successful pregnancy. Eighty percent of the first postpartum ovulations result in a new pregnancy (Ziegler, 1987a). Thus, in successful captive breeding colonies of cotton-top tamarins the average inter-birth interval is 29 weeks (Snowdon et al., 1985).

Cotton-top tamarins do not exhibit seasonal patterns of reproduction in most captive colonies housed under artificial lighting and temperature conditions. In wild populations, there is usually a seasonal birth peak associated with the onset of the rainy season (Savage, 1990; Savage et al., 1996). However, wild-caught captive groups kept in outdoor enclosures in their native habitat have inter-birth intervals similar to the 29 weeks found in the captive colonies suggesting that diet may regulate fertility in the wild (Savage, 1990).

Ovarian Cycle

The ovarian cycle of the cotton-top tamarin is approximately 20 days in length (Brand, 1981; French et al., 1983; Ziegler et al., 1993). There are no physical signs of ovulation that are readily detectable by human observers, however studies have shown that there are olfactory cues in the scent secretions and urine of female cotton-top tamarins that are readily detectable by their mates (Ziegler et al., 1993). Copulations are not restricted to the time of ovulation, as evidenced by the continuous receptivity of females to males throughout the entire reproductive cycle (French, 1984; Savage et al., 1988).

 Puberty and Puberty Acceleration

Although the onset of puberty is between 15-17 months in cotton-top females that remain in their natal group, it can be accelerated by exposure to a novel male to as early as 10 months (Ziegler, 1987b). Females removed from their natal group at an early age and paired with an unfamiliar adult male will exhibit an acceleration of puberty and the rapid onset of ovarian cycles (French et al., 1983; Ziegler, 1987b). However, at this early age, most females have not had sufficient infant caretaking experience to successfully raise their own offspring. Thus, although a cotton-top female may be physiologically mature at 10 months of age, she lacks the social experience necessary to successfully rear her offspring.

 Suppression of Fertility

The reproductive biology of the female cotton-top tainarin is significantly influenced by her social environment. As long as a female (daughter) remains in her natal group, her ovarian cycles will be suppressed. Suppression of fertility in the natal group has been observed in cotton-top females as old as 44 months (French et al., 1984). Although suppressed females do have detectable levels of estrogen and luteinizing hormone, indicating that they are reproductively mature, their hormones are at unusually low levels and are acyclic. Removal from the family and pairing with an unfamiliar male is necessary to initiate normal ovarian cycles in cotton-top females. Although isolation from the natal group elevates hormone levels, normal ovarian cycles are not established until the female is paired with a novel male (Savage et al., 1988; Widowski et al., 1992; Ziegler, 1987b). Although close (within 15 cm) exposure to a novel male, including a combination of auditory, olfactory and particularly visual contact may be enough to stimulate ovulation in most cotton-top females, auditory and olfactory contact alone are not enough to stimulate ovulation (Widowski et al., 1990; 1992). Scent secretions mixed with urine from the natal group will delay the initiation of normal ovarian cycles (Savage et al., 1988). However, once normal cycles are established, they cannot be suppressed by exposure to scent secretions (Savage et al., 1988).

 Reproductive Senescence

Older (14-16 years) cotton-top tamarin females may experience some irregularity of cycles, yet true reproductive senescence does not begin until approximately 17 years of age (Tardif & Ziegler, 1992). Although cotton-tops over 17 years are anovulatory, hormone levels are moderate and the steroidogenic luteal cells are still functional, despite a lack of follicular development (Tardif & Ziegler, 1992). This is substantially different from the pattern in Old World primates, where the cessation of follicular development in reproductive senescence is associated with substantial decrease in steriodogensis (Tardif & Ziegler, 1992). Although testosterone levels and sperm counts have not been systematically evaluated in this species, males appear to be capable of siring offspring throughout their lifetime, with little evidence of reduced fertility with age.

 Contraception

The Cotton-top Tamarin SSPÓ in coordination with the AZA Contraception Advisory Group have recommended certain methods for contracepting cotton-top tamarin females. Development and testing of effective means of contraception for this endangered species continues to occur. Cooperation in providing information that allows the evaluation of the current contraceptive recommendations is desperately needed. Please refer to Appendix 1 in the Veterinary Care chapter.

Any cotton-top tamarin female who is to be contracepted should receive the MGA implant available from Dr. Ed Plotka (for order form, refer to Appendix 2 in the Veterinary Care chapter). If the female recommended for contraception is pregnant, she should be given 10 mg/kg DepoProvera within 10 days postpartum. Once the infants are weaned (14-16 weeks), an MGA implant can be inserted. If an adult female is in a family group that contains daughters and must be contracepted, do not remove her from the group for more than 24 hours, as daughters may compete with their mother for the breeding position upon her return. Daughters greater than 14 months of age who are in groups containing an unrelated breeding adult male should receive an MGA implant for as long as they remain in the group.