Infant Mortality in Black-and-Gold Howlers (Alouatta caraya) Living in a Flooded Forest in Northeastern Argentina

Abstract

Ecological and social factors have a significant effect on infant survivorship in nonhuman primates. We present 6293 group-months of infant birth and mortality data for 29 groups of Alouatta caraya inhabiting a flooded forest in northeastern Argentina, collected over 1.5-8 yr depending on the group. We tested whether infant mortality was a response to the effects of flooding on food availability and whether male takeovers resulted in greater opportunities for infanticide. During our study, 43 of 113 infants died at a mean age of 5 mo. In 24 cases the cause of death was unknown. In the remaining 19 cases infant deaths were attributed to periods of intense flooding (N08), replacement of the breeding male (N08), problems associated with birth (N02), and injuries during an intergroup encounter (N01). Flooding reduced the availability of mature leaves, which appeared to play an important role in the ability of mothers to nurse their offspring. Male replacements occurred in four social groups that contained only one fully adult male. Infant mortality was significantly higher in groups that experienced male replacement compared to groups without male replacement. These results indicate that infant mortality in Alouatta caraya is affected by several factors-natural disasters, maternal condition and food availability, infanticide after male replacement, and possibly disease and predationeach of which needs to be evaluated to understand the history and demography of this primate population.

Infanticide as Sexual Conflict: Coevolution of Male Strategies and Female Counterstrategies

“…In a sample of 29 primate populations in which infanticide is known, 19 had relative rates !30% (Palombit 2012). In some of these taxa, male replacement produces a 3-, 11-, or 32-fold increase in infant mortality (Beehner and Bergman 2008;Fedigan et al 2008;Pavé et al 2012). In sciurid rodents, male (as well as female) infanticide is a major cause of infant and juvenile mortality (Ebensperger and Blumstein 2007).…”

Howler Monkeys

“…Clarke and Glander ( 1984 : 123) similarly suggest that female A. palliata "should vary [their] reproductive tactics" according to ecological and social conditions that infl uence infant survivability. Pavé et al ( 2012 ) support this viewpoint by demonstrating a spike in infant mortality during a 2-month period of fl ooding that drastically reduced food availability (8 of 40 infants [mean age: 4 months] died). These authors suggest that mothers stopped investing in offspring when the infants' chances of survival became low (Pavé et al 2012 ).…”

“…Pavé et al ( 2012 ) support this viewpoint by demonstrating a spike in infant mortality during a 2-month period of fl ooding that drastically reduced food availability (8 of 40 infants [mean age: 4 months] died). These authors suggest that mothers stopped investing in offspring when the infants' chances of survival became low (Pavé et al 2012 ). Ateles and Lagothrix females may not have the same opportunity to shift their investment: because they produce fewer offspring in their lifetimes, their reproductive success may depend more on the survival of the current offspring, even if it diminishes their future reproductive efforts (Raguet-Schofi eld 2010 ).…”

Insights into Reproductive Strategies and Sexual Selection in Howler Monkeys

“…Differences in mean interbirth interval among species and populations might be attributed to differences in seasonal abundance and quality of food resources across diverse habitats, as was suggested for a 2-month mean difference in the interbirth interval between A. arctoidea populations inhabiting woodland versus gallery forests (Crockett and Rudran 1987 ). Furthermore, when a female loses an infant younger than 1-year old, the period of postpartum acyclicity ends abruptly and the female starts soliciting sexual interactions from 1 day to 3 weeks after the loss of the infant (Glander 1980 ;Van Belle et al 2009 ), signifi cantly shortening the interbirth interval to an average of 11.3 months (Crockett and Sekulic 1984 ;Fedigan and Rose 1995 ;Crockett 2003 ;Pavé et al 2012 ). Dias et al ( 2011 ) This shortening of the interbirth interval after the premature death of an unweaned young infant is the major evidence supporting the adaptive value of infanticide committed by males (Struhsaker and Leland 1987 ;van Schaik and Janson 2000 ;Crockett 2003 ).…”