. Patterns of participation and free riding in territorial conflicts among ringtailed lemurs

Looking into individual variation in territorial defense among female ringtailed lemurs, subjects at Duke University Primate Center in two groups were studied. To identify the location of individuals relative to aggressive territorial conflict, there were three zones identified progressively closer to the territorial boundary.


 Different acts were recorded, such as aggressive (bite, cuff, chase, lunge, and grab), submissive (spat, flee, jump away, and cower) and affiliative (touch, body/face greet, lick, play). There were also self directed behaviors. Group size may influence patterns of individual participation, with free riding thought to be more common in larger groups.



Also, there were potentials for increased risk of injury, increased risk of overheating, and behavioral indicators of stress. Individuals may also provide incentives, such as grooming, to encourage other animals to participate in territorial defense. However, individuals that participated in aggressive intergroup interactions were not more likely to receive affiliative acts from group mates during encounters.



Additional unexplained variation may be accounted for by patterns of policing, in which free riders are punished for failing to participate in territorial defense. During inter-group encounters, however, within-group aggression among females was uncommon, with only four aggressive acts observed among individuals of the same group. The rate of aggression appeared to increase slightly in the thirty minutes after encounters ended, but it was not significantly different from the rate of aggression in the thirty minutes before encounters started. On an individual basis, There was no statistical association between rates of aggressive acts to the other group during encounters and rates of aggressive acts toward group mates found or received from group mates following encounters.

  
    Nunn, C. and Deaner, R. Patterns of participation and free riding in territorial conflicts among ringtailed lemurs (Lemur catta). Behavioral Ecology and Social Biology. Vol 57, No. 1, 50-61.

Male Mate Choice in Lemur catta

Generally, females are the more selective sex because of their greater parental investment. However, it would benefit males to exercise mate choice for two reasons: (1) if male reproductive success is limited by more factors than simply the number of female mates and (2) if females differ in quality- or more specifically in their reproductive potential. Both of these factors must be in place for the male mate selection to be evolutionary advantageous.

If females differ in reproductive potential, males might exercise some degree of mate choice because of one or more factors that put an upper limit to male reproductive success. Males must operate under time constraints, as well as possibly dwindling energy or sperm reserves, or both. Males that exercise mate selectivity might therefore have a reproductive advantage by allocating their time, sperm, and energy wisely. Given the reproductive characteristics of the species, male mate selectivity is theoretically probable, as the criteria
that would select for male mate selectivity appear to be in place in Lemur catta.

A mother with her offspring. The father doesn't do much to help raise them.

Sperm depletion is another potential limiting factor for male reproductive success, for female ring-tailed lemurs cycle asynchronously, but in close temporal proximity. All troop females enter estrus within 1–3 wk of one another. Even if a male mates only once with each female that comes into estrus, he can potentially ejaculate many times per wk during the short breeding period. In the wild, males mate with extratroop females, which even further increases a male’s number of potential mates, and ejaculations, over a short time. Whether or not frequent ejaculations in ring-tailed lemurs can lead to notably decreased sperm reserves enough to limit male reproductive success appreciably is open to debate. Lemur catta males may be evolutionarily adapted to ejaculate frequently and produce adequate amounts of sperm over a short time.

For male mate selectivity to be adaptive, it is not enough that one or more factors limit male reproductive success. Females must also differ among each other with respect to mate quality—more specifically, their reproductive potential. Female fecundity differs among individuals as a function of one or more traits, such as dominance status. The highest-ranking female in a troop is responsible for the greatest number of agonistic interactions, most of which are over priority of access to food resources.

In traditional investigations of mate choice in females, scoring mating preferences requires that females reject some males as mates and accept others. However, one cannot apply the scoring system to male ring-tailed lemurs because they do not decline opportunities to mate with a female unless it is during the day of a female’s estrus, and they have already ejaculated once with her. Because males are less selective in their sexual preferences than females does not mean that it male mate choice does not occur.


Consequently, only females for which estrus was observed with at least one or more male mounting with intromission contributed to the analyses. Males aggressively mate guard females before and after mating, and other males frequently harass them during copulation, which involves several mounts with intromission before ejaculation. Given the strong correlation between female reproductive success and dominance status in 2000 when the two matrilines comprised the troop, males may expend the greatest mating effort for females that have high reproductive success, high dominance status, or both.

Using male mating effort as a proxy for male mate choice, it was found that males did not prefer all females equally as mates; they expended significantly more male-male aggression during the estrus of only certain females.

  Parga, J. Male Mate Choice in Lemur catta. International Journal of Primatology. Vol 27, No. 1, 107-131

Development of Olfactory Behavior in Captive Ring-tailed Lemurs (Lemur catta)

A long term research project was conducted on developmental aspects of olfactory behavior in ring-tailed lemurs to document  the ontogenetic sequence of olfactory of behavior. The olfactory communication system of ring-tailed lemurs is extremely complex. It consists of investigative and scent- marking behaviors and plays an important role either with regard to intertroop territorial defense or to regulation of the relationships within groups.

Although both males and females mark anogenitally, females have a greater number of anogenital scent glands than males.  However, females lack the antebrachial and brachial organs specialized for scent production in males. The secretions produced by the male organs are used either to mark items in the environment or for tail-anointing.

A study was conducted from March 1996 to June 1999 on a colony of lemurs from the Pistoia Zoo (Italy). Divided into two groups, there were 5 infant males and 4 infant females, 7 adolescent males and 4 adolescent females. Preliminary observations ad libitum allowed us to confirm the duration limits of infancy (0–6 mo), subdivided into lactation (0–15 weeks) and weaning (16–26 weeks), the juvenile phase (7–15 mo) and adolescence (16–18 mo). We observed first copulation in a female a t 22 months of age.

The scores were as grooming, locomote, and play. Vocalization was not scored. Countermarking indicates any kind of marking (wrist, wrist-to-pit, and genital mark) deposited over the scent marks of other individuals. We recorded countermark and investigation bouts (both sniffing and licking) of anothers’ scent marks only when they happened soon after mark deposition.

RESULTS

In the weaning stage, tail play was the only scent-marking behavior performed by infant males. In the first 2 weeks of life, infants were carried by their mothers so that a continuous olfactory smell was possible. Allmost in the middle of the juvenile period (around twelve months) brachial and antebrachial marking (wrist) appeared.

 

On the whole, olfactory investigation matured earlier than scentmarking; it was already present during infancy, while marking began only during the second half of the juvenile period. There was no significant difference between olfactory behavior in males and females.


Palagi, E. et al. (2001) Development of Olfactory Behavior in Captive Ring-tailed Lemurs (Lemur catta). International Journal of Primatology, Vol 23, No. 3, 587-599.