Young Lemurs Research Articles

Organizational and activational androgens, lemur social play, and the ontogeny of female dominance

The role of androgens in shaping “masculine” traits in males is a core focus in behavioral endocrinology, but relatively little is known about an androgenic role in female aggression and social dominance. In mammalian models of female dominance, including the ring-tailed lemur (Lemur catta), links to androgens in adulthood are variable. We studied the development of ring-tailed lemurs to address the behavioral basis and ontogenetic mechanisms of female dominance. We measured behavior and serum androgen concentrations in 24 lemurs (8 males, 16 females) from infancy to early adulthood, and assessed their ‘prenatal’ androgen milieu using serum samples obtained from their mothers during gestation. Because logistical constraints limited the frequency of infant blood sampling, we accounted for asynchrony between behavioral and postnatal hormone measurements via imputation procedures. Imputation was unnecessary for prenatal hormone measurements. The typical sex difference in androgen concentrations in young lemurs was consistent with adult conspecifics and most other mammals; however, we found no significant sex differences in rough-and-tumble play. Female (but not male) aggression increased beginning at approximately 15 months, coincident with female puberty. In our analyses relating sexually differentiated behavior to androgens, we found no relationship with activational hormones, but several significant relationships with organizational hormones. Notably, associations of prenatal androstenedione and testosterone with behavior were differentiated, both by offspring sex and by type of behavior within offspring sexes. We discuss the importance of considering (1) missing data in behavioral endocrinology research, and (2) organizational androgens other than testosterone in studies of female dominance.

AGE-RELATED CHANGES IN HEMATOLOGY AND BLOOD BIOCHEMISTRY VALUES IN ENDANGERED, WILD RING-TAILED LEMURS ( LEMUR CATTA) AT THE BEZÀ MAHAFALY SPECIAL RESERVE, MADAGASCAR.

The health of 44 wild ring-tailed lemurs ( Lemur catta) at the Bezà Mahafaly Special Reserve was assessed across three age classes: <5 yr (young), 5-9 yr (adult), and ≥10 yr (old). Hematology and biochemistry tests were performed manually (leukocyte count and differential, packed cell volume, total protein) and using a point-of-care analyzer (hematocrit, hemoglobin, glucose, blood urea nitrogen, creatinine, sodium, potassium, chloride, ionized calcium, total carbon dioxide, anion gap), respectively. Urine specific gravity was measured via refractometry. Age- and sex-related differences were detected. Old lemurs had significantly lower lymphocyte count than adult and young lemurs, leading to markedly lower total leukocyte count and higher neutrophil-to-lymphocyte ratio. Decreased lymphocyte count with advanced age is consistent with immunosenescence. Young lemurs had significantly higher total protein, monocyte count, and potassium than adult and old lemurs but significantly lower ionized calcium than adult lemurs. Males had significantly higher leukocyte, neutrophil, and monocyte counts; lower percentage basophils; and higher blood urea nitrogen than females. Females had markedly higher glucose than males. Young females had the highest monocyte count and total protein, which were significantly lower in the adult and old age classes. Basophil count was stable in females across age but dropped precipitously in males in the adult and old age classes. Within adult and old age classes, males had significantly higher blood urea nitrogen and lower basophils than females. Glucose was significantly higher after α2 agonist administration. Identifying age-related hematologic and biochemical changes in apparently healthy wild ring-tailed lemurs will aid in clinical diagnosis and treatment of lemurs in human care, which is especially relevant for management of geriatric animals in zoo populations. Equally important, a better understanding of the ability of aging lemurs to tolerate environmental stressors will inform the capacity for this species to cope with ongoing and future habitat alteration.

Field Anesthesia of Wild Ring-tailed Lemurs (Lemur catta) Using Tiletamine–Zolazepam, Medetomidine, and Butorphanol

Telazol has been commonly used for field anesthesia of wild lemurs, including ring-tailed lemurs (Lemur catta). Telazol alone provides good induction, but doesn't cause adequate muscle relaxation and sedation for collecting consistent somatic measurements and high-quality dental impressions that are sometimes needed. Variability in induction response has been seen between individuals that have received similar dosages, with young lemurs seeming to need more anesthetic than mature lemurs. This investigation evaluated Telazol induction in young (2.0-4.9 yr) and mature (> or = 5.0 yr) ring-tailed lemurs and compared postinduction supplementation with medetomidine or medetomidine-butorphanol. Forty-eight lemurs were anesthetized with Telazol administered via blow dart; then, 20 min after darting, they were supplemented via hand injection with either medetomidine (0.04 mg/ kg) or medetomidine-butorphanol (0.04 mg/kg and 0.2 mg/kg, respectively). The odds ratio for young lemurs to need more than one dart for induction, relative to mature lemurs, was 3.8, even though the initial dose of Telazol received by young lemurs (19 +/- 7 mg/kg) was significantly higher than the initial dose administered to mature lemurs (12 +/- 5 mg/kg). The total Telazol dosage was also significantly different between young lemurs (33 +/- 15 mg/kg) and mature lemurs (18 +/- 9 mg/kg). Both medetomidine and medetomidine-butorphanol provided good muscle relaxation and sedation for all procedures. Physiologic values were similar between the two protocols. Oxygen saturation by pulse oximetry was generally good, although there were a few SaO2 values < 90%. Recoveries were smooth, but long. Time to head up was correlated with total Telazol dosage in mature lemurs. In young lemurs, time to standing was correlated with Telazol induction dosage and time of last Telazol administration. Lemurs that received hand injections of Telazol took longer to recover than those that did not. Further refinements are needed to increase induction reliability and to decrease recovery time, particularly in young lemurs.

Mother-Young Feeding Synchrony and Early Food Selection Differences in Eulemur fulvus

I tested the hypothesis that mother-young cofeeding correlates with a systematic similar food selection in wild Mayotte brown lemurs (Eulemur fulvus). I simultaneously recorded the feeding behavior of 4 maternal dyad members, from infant birth to weaning, and 10–12 mo of juvenile age, during 10-min focal periods, each separated by 5-min intervals over 10 mo. I recorded the solid food items selected for each feeding behavior at the level of specific plant part, along with the distance between the 2 individuals. I considered feeding behaviors simultaneous (between the young lemurs and their mothers) when the young began to eat a food item while the mother was already eating, regardless of the separation distance. During their first year, most of the feeding events of the young brown lemurs were initiated by their mothers. However, infants also selected different food items from those chosen by their mothers in almost one-third of cases, and the food selection dissimilarity was not attributable to an increase in the distance of separation. For juveniles, dissimilar food selection was significantly lower and linked to an increase in mother-juvenile separation distance. Thus, the substantial proportion of dissimilarity in solid foods selected by the infant during the synchronized feeding behaviors strongly suggests that social influences were not food-specific and might instead drive the acquisition of group feeding activity rhythm rather than food selection habits.

Protective effect of alpha lipoic acid and trans resveratrol on spatial memory deficits caused by intracerebroventricular streptozotocin in rats

while eliciting variable immune response and reducing brain amyloid burden to different degrees (J. Neurosci. 24, 2004). Objective(s): 1) To determine the therapeutic benefit of K6A 1-30 in 2 year old Tg2576 mice with treatment starting at 11vs. 19 months. 2) To assess the immune response and therapeutic effect of our vaccines in Microcebus murinus, a lemur primate that develops plaques and tangles as seen in AD. Methods: Mice were immunized with K6A 1-30 in alum adjuvant which promotes a humoral immune response. At 2 years of age, sensorimotor and cognitive tests were performed, and brains then processed for amyloid burden measurements. Young lemurs were immunized with A 1-42 and several nontoxic A homologs in alum and bled at various time points between injections. Older lemurs are currently going through behavioral assessment prior to vaccination. Conclusions: In the mice, K6A 1-30 improved cognition when therapy was initiated at 11 months but not at 19 months. Amyloid burden analysis is underway. Cerebral bleeding has not been observed in brains from mice with high antibody titer examined so far. In the lemurs, all the peptides elicited a moderate to robust IgM titer. A 1-42 and K6A 1-30 resulted in a high IgG titer similar to the mouse response. A 1-30[E18E19] produced a low IgG reponse as in the mouse. K6A 130[E18E19] gave rise to a strong IgG titer whereas in the mouse this derivative elicited a low IgG titer. Bleeds at 5 months after last injection are in progress. The mouse findings indicate that immunotherapy at an old age may not be beneficial. The immune response in the mouse vs. the lemur primate differs for some of the A homolog vaccines.

Handedness as a function of sex and age in a large population of Lemur..

A population of 194 lemurs (Lemur spp.), 116 males and 78 females, from 1 to 30 years of age, was assessed for lateralized hand use in simple food reaching with a minimum of 100 reaches per animal. A hand preference was present in 80% of the population with a bias for use of the left hand that was most characteristic of male lemurs and young lemurs. The results confirm the presence of lateralization in prosimians, and we interpret the sex and age differences in relation to current theories of neural lateralization.