Reproductive biology of the slender loris (Loris lydekkerianus lydekkerianus)

The slender loris (Loris lydekkerianus lydekkerianus), a nocturnal prosimian, was studied for 21 months in its natural habitat of scrub jungle in Dindigul, south India. Here we report on its reproductive biology. Identified and unidentified lorises were observed for a total of 2,656 h. Reproductive seasonality was seen, with births and oestrus observed to be highest in April-June and October-December. The mating system was promiscuous with 1 female mating successively with 3-4 males. A gestation period of 5.5 months and an inter-birth interval of 7 months were recorded. Adult females had a reproductive potential of 4 infants per year. The findings presented in this paper constitute the first information on the life history parameters of wild slender lorises.     

Parturition in the slender loris (Loris tardigradus lydekkerianus)

The process of the birth of an infant slender loris has been observed under caged conditions—probably for the first time. The total time taken for the complete emergence of the fetus was 4 min and 34 sec. Three hours and 4 min later, the placenta was expelled and was completely devoured by the mother. Both head and breech presentations are normal and involve no manipulation from the mother. Detailed observations have been made on the pre-parturitional and post-parturitional changes in the mother.     

Spacing system of the Mysore slender loris (Loris lydekkerianus lydekkerianus)

Loris lydekkerianus lydekkerianus has been shown to have a promiscuous copulatory pattern, to maintain social networks via frequent loud calls, to interact socially throughout the night with all age classes, and to sleep socially. Though these behaviors point towards a multimale social system, no study of their spacing system has yet been provided to support this view. From October 1997-August 1998, I conducted a study of the Mysore slender loris in Ayyalur, India. During 1,400 field hours, data were collected on range use of 3 adult females, 3 adult males, 1 subadult female, and 1 subadult male. Lorises slept in groups averaging 4 individuals, composed of an adult female, her offspring, and 1-2 adult and subadult males. Sleeping sites for three groups were located within 1.9 ha in the center of the study area. The minimum convex polygon in hectares encompassing each animal's range was determined, as well as overlap among home ranges of individual lorises. Average home range sizes were: adult males, 3.6 ha +/- 0.09; subadult/smaller males, 1.17 ha +/- 0.26; and adult and subadult females, 1.59 ha +/- 0.24. Male ranges overlapped with at least 2-3 other adult males (0.72 ha +/- 0.23). Female ranges overlapped slightly with at least 2 other female ranges (0.22 ha +/- 0.25). Male ranges overlapped those of at least 3 females (0.82 ha +/- 0.51). Patterns of home range and sleeping site support previous suggestions of a multimale social system, similar to aye ayes and some galagos.     

Mother-infant relationship in the slender loris (Loris tardigradus lydekkerianus)

Close observations under caged conditions were made on the behaviour of four mother lorises towards their own and alien infants. There appears to be no mutual recognition between the mother and her infant, and the relationship appears to be less specific. The infants are accepted by and get settled with any lactating female. In the first few weeks after birth, there is an intense attachment exhibited by the mother towards her baby. When the baby is separated, it exhibits a series of “fixed action patterns.” As the infant grows older, maternal interest declines and is lost after about 15–20 weeks post partum. Vocalization of the separated juveniles evokes greater maternal response than the visual cue.     

Reproduction in the slender loris (Loris tardigradus malabaricus)

A breeding colony of slender lorises (Loris tardigradus malabaricus) was studied to obtain data for comparison with other prosimian species, to contribute reproductive information for improving management of captive lorises, and to resolve some uncertainties in the literature regarding reproduction in the slender loris. At the Duke University Primate Center, a female slender loris reached sexual maturity at approximately ten months of age and conceived at one year of age. The length of the estrous cycle was 29–40 days, with copulation occurring over two consecutive days during estrus. Gestation length was 166–169 days. Litter size for each six births was one. Conception did not occur during an immediate post-partum estrus, but four months after birth, resulting in a 9 1/2-month interbirth interval. There was no evidence of reproductive seasonality. Lactation lasted between five and seven months. Reproductive rates of slender lorises are among the lowest of primates less than 500 g. Differences in reproductive parameters may exist between different subspecies of slender lorises.     

Home range and ranging pattern in the slender loris(Loris tardigradus lydekkerianus)

The home range and ranging pattern of the slender loris (Loris tardigradus lydekkerianus) was studied for 21 months in a scrub jungle in Dindigul, Tamil Nadu, south India. Sixteen individuals were observed for a total of 2261 hours. Home ranges were measured for eight adult individuals and eight juvenile and subadult individuals. Males had significantly larger home ranges than the females, and home range size increased post-weaning. The ranging patterns involved minimal female intrasexual overlap, large male intrasexual overlap and large intersexual range overlap.     

Foraging behaviour of the slender loris (Loris lydekkerianus lydekkerianus): implications for theories of primate origins

Members of the Order Primates are characterised by a wide overlap of visual fields or optic convergence. It has been proposed that exploitation of either insects or angiosperm products in the terminal branches of trees, and the corresponding complex, three-dimensional environment associated with these foraging strategies, account for visual convergence. Although slender lorises (Loris sp.) are the most visually convergent of all the primates, very little is known about their feeding ecology. This study, carried out over 10 (1/2) months in South India, examines the feeding behaviour of L. lydekkerianus lydekkerianus in relation to hypotheses regarding visual predation of insects. Of 1238 feeding observations, 96% were of animal prey. Lorises showed an equal and overwhelming preference for terminal and middle branch feeding, using the undergrowth and trunk rarely. The type of prey caught on terminal branches (Lepidoptera, Odonata, Homoptera) differed significantly from those caught on middle branches (Hymenoptera, Coleoptera). A two-handed catch accompanied by bipedal postures was used almost exclusively on terminal branches where mobile prey was caught, whereas the more common capture technique of one-handed grab was used more often on sturdy middle branches to obtain slow moving prey. Although prey was detected with senses other than vision, vision was the key sense used upon the final strike. This study strongly supports the notion that hunting for animal prey was a key ecological determinant in selecting for visual convergence early on in primate evolution. The extreme specialisations of slender lorises, however, suggest that early primates were not dedicated faunivores and lend further support to the emerging view that both insects and fruits were probably important components of the diet of basal primates, and that exploitation of fruits may account for other key primate traits.     

Observations of mating, birthing and parental behaviour in three subspecies of slender loris (Loris tardigradus and Loris lydekkerianus ) in India and Sri Lanka

Studies of the life history parameters of slender lorises in captivity have led to conflicting results regarding gestation length, birth seasonality, interspecies variation in litter size and the degree of parental care given to offspring. During the course of field studies of Loris lydekkerianus lydekkerianus, L. l. nordicus and L. tardigradus tardigradus, data were collected on these life history variables, as well as on behaviours relating to mating. All 3 taxa displayed courtship behaviour involving the pursuit of a female by multiple males. Mating corresponded closely with captive observations, with a period of prolonged single intromissions lasting 3-11 min. One gestation period of 163 days was calculated for L. l. lydekkerianus. Births for all 3 taxa were distributed throughout the year, and males were seen mating throughout the year. All 3 taxa gave birth to singletons and twins; no subspecific pattern in litter size was evident. Females carried infants for the first 4 weeks of life and were regularly attended by males, which groomed both the mother and her offspring. After infants had been parked, female L. l. lydekkerianus and L. l. nordicus rarely returned before dawn, though males visited and played with infants. Female L. t. tardigradus maintained proximity with their infants, whilst males were not observed in proximity to infants during the night. All 3 taxa slept in social groups. High-energy milk, in combination with male care, may aid in the potentially high reproductive output of 4 infants per year.     

Social behaviour of the slender Loris (Loris tardigradus lydekkerianus)

The social behaviour of the nocturnal prosimian Loris tardigradus lydekkerianus in its natural habitat was studied for 21 months in a scrub jungle in Dindigul, southern India. A total of 22834 scans were collected during 2656 hours of observation on identified and unidentified lorises. Social interactions were observed between individuals of all age-sex classes, both during the night and at dawn, when the animals met to sleep together. The majority of aggressive encounters between individuals occurred in territorial and mating contexts. Individuals also communicated with each other through chemical and vocal signals. Adults and sub-adults of both sexes were observed to immigrate into the study area, leading to social interactions with resident individuals.     

Polycystic nephropathy in slender lorises (Loris lydekkerianus)

In a colony of slender lorises, 20 deaths that occurred over a period of 11 years were investigated postmortem. Juvenile/adult polycystic nephropathy was observed in one newborn and 13 adult slender lorises. Although polycystic kidney disease (PKD) in humans and other animals is known to be inherited, it is not clear whether kidney alterations in slender lorises are genetically transmitted, stress related, or induced by microbiological influences.     

Thermoregulation in the slender loris (Loris tardigradus)

Thermoregulatory characteristics of slender lorises largely resemble those of other slow-moving Lorisidae: Body temperature is slightly below the normal mammalian level and basal metabolic heat production is only about half of the mass-specific standard. During cold exposure only a rather small body core is kept at a high temperature level whereas large parts of the body are allowed to cool. Contrary to the findings in other Lorisidae slender lorises are more tolerant against high environmental temperatures, largely due to the ability of considerably increasing evaporative cooling.     

Locomotor mechanics of the slender loris (Loris tardigradus)

The quadrupedal walking gaits of most primates can be distinguished from those of most other mammals by the presence of diagonal-sequence (DS) footfall patterns and higher peak vertical forces on the hindlimbs compared to the forelimbs. The walking gait of the woolly opossum (Caluromys philander), a highly arboreal marsupial, is also characterized by diagonal-sequence footfalls and relatively low peak forelimb forces. Among primates, three species--Callithrix, Nycticebus, and Loris--have been reported to frequently use lateral-sequence (LS) gaits and experience relatively higher peak vertical forces on the forelimbs. These patterns among primates and other mammals suggest a strong association between footfall patterns and force distribution on the limbs. However, current data for lorises are limited and the frequency of DS vs. LS walking gaits in Loris is still ambiguous. To test the hypothesis that patterns of footfalls and force distribution on the limbs are functionally linked, kinematic and kinetic data were collected simultaneously for three adult slender lorises (Loris tardigradus) walking on a 1.25 cm horizontal pole. All subjects in this study consistently used diagonal-sequence walking gaits and always had higher peak vertical forces on their forelimbs relative to their hindlimbs. These results call into question the hypothesis that a functional link exists between the presence of diagonal-sequence walking gaits and relatively higher peak vertical forces on the hindlimbs. In addition, this study tested models that explain patterns of force distribution based on limb protraction angle or limb compliance. None of the Loris subjects examined showed kinematic patterns that would support current models proposing that weight distribution can be adjusted by actively shifting weight posteriorly or by changing limb stiffness. These data reveal the complexity of adaptations to arboreal locomotion in primates and indicate that diagonal-sequence walking gaits and relatively low forelimb forces could have evolved independently.     

Activity budget and positional behavior of the Mysore slender loris (Loris tardigradus lydekkerianus): implications for slow climbing locomotion.

Both predator defense and feeding ecology models have been proposed to explain the relatively slow climbing locomotion of the Lorisinae. During a study of the socioecology of the Mysore slender loris (Loris tardigradus lydekkerianus) in Tamil Nadu, India, six categories of behavior and eleven different postures were recorded to estimate a general activity budget for the slender loris, and are examined here particularly in relation to slow climbing locomotor strategies. Reactions to potential predators are also described. The main study population was composed of 15 animals. Activity budgets were compiled in three ways: all instantaneous point samples collected over 1,173 h pooled (n = 13,717), the means of individual lorises (n = 15) and behavior at the moment of first contact (n = 357). No significant difference was found between these three data sets. Approximately 45% of the activity budget was spent in inactive behaviors including sitting vigilant, resting and sleeping. Foraging and traveling comprised nearly half the activity budget, with the rest of the time spent grooming. The most common postures assumed by lorises were sitting and quadrupedal walking. Individual lorises were relatively gregarious and spent up to half their activity budget with other animals. Unlike pottos and angwantibos, lorises did not freeze, head butt or drop from branches in reaction to potential predators, but either ignored them, fled or made loud calls. Cryptic and slow climbing locomotion were used before traveling on open ground between discontinuous substrates, thereby supporting hypotheses relating to predator pressure, and also before capturing fast moving insect prey, supporting hypotheses relating to diet. It is proposed that a divergence in foraging strategies between bushbabies and lorisines may be the best adaptive explanation for their behavioral and morphological differences, including predator defense mechanisms.     

Distribution and Conservation of Slender Lorises (Loris tardigradus lydekkerianus) in Southern Andhra Pradesh,South India

Slender lorises live in forests of southern India and Sri Lanka. Little is known about their distribution patterns and relative densities. We report the results of a survey conducted in 6 forest divisions in the southern parts of the state of Andhra Pradesh, South India. Relatively high densities of lorises occurred in mixed deciduous forests and in adjoining farm lands interspersed with trees. Three distinct populations inhabit the study area. We recommend conservation measures for Loris tardigradus.     

A new species of Beilschmiedia (Lauraceae) from the Western Ghats,India

Beilschmiedia tirunelvelica is described and illustrated as a new species from the Western Ghats of Agasthiyamalai Biosphere Reserve, India. The differences to similar taxa are provided with dichotomous key and table.     

A new species of Eugenia (Myrtaceae) from the Western Ghats, India

Eugenia shettyana, is described and illustrated as a new species from the Western Ghats, India. The differences to similar taxa are discussed.