Effects of forest fragmentation on the dietary ecology and activity of a nocturnal lemur community in North West Madagascar.

Deforestation and habitat fragmentation is the primary threat to primate populations. The primates that live within degraded and anthropogenically disturbed habitats typical of fragmented landscapes have to cope with lower availability of resources in comparison to primates in continuous, undisturbed forests. While some species are sensitive to forest fragmentation, some evidence exists to suggest that primates can alter their behavior and adapt to such changes, which enables their survival in suboptimal habitat. In this study, we assessed how forest fragmentation and its associated edge-effects impact the feeding ecology and activity levels of a nocturnal primate community in the Sahamalaza-Iles Radama National Park, North West Madagascar. From March 06, 2019 to May 17, 2022, we collected data on tree and invertebrate phenology at our study site, and feeding ecology and activity for 159 lemur individuals from four species. Fruit and flower availability varied significantly between continuous and fragmented forest, and between forest core and edge areas, with continuous forest exhibiting higher continuous fruit and flower availability. Lemur feeding ecology varied significantly too, as the feeding niches of all four species were significantly different between continuous and fragmented forest and between core and edge areas. However, lemur activity levels were mostly consistent among all forest areas. The results of this study suggest that nocturnal lemurs are able to adapt their dietary ecology in response to the available food sources within their habitat. Due to this flexible ecology and dietary plasticity, the lemurs do not need to significantly alter their behavior in different environments to fulfill their dietary needs. While nocturnal lemurs demonstrate adaptability and flexibility to degraded habitat, it is unclear how far this plasticity will stretch considering that Madagascar's forests are still being cleared at an alarming rate. Urgent conservation action is therefore needed to ensure the future of lemur habitat.

Habitat and ecological niche characteristics of the elusive Hairy-eared Dwarf Lemur (Allocebus trichotis) with updated occurrence and geographic range data.

Ecological niche modeling (ENM) is particularly useful in the study of cryptic and elusive species that are only rarely seen, difficult to study in the wild, and simultaneously threatened by a multitude of anthropogenic factors. We collected presence records one such example, the understudied Hairy-eared Dwarf Lemur (Allocebus trichotis), from the literature and supplemented these with observations from surveys in previously unstudied areas to model its fundamental and realized niche throughout Madagascar. We further evaluated habitat characteristics at each sighting location to judge its conservation status and its adaptability toward habitat degradation. We found 31 presence localities in the literature and directly observed A. trichotis a further 23 times. According to the ENMs, precipitation of the driest quarter and maximum temperature of the warmest month mostly influenced its distribution, restricting it to the higher altitudes of the northeastern humid forests of Madagascar. Its fundamental niche, extent of occurrence, and area of occupancy were estimated as 65,819, 53,054, and 16,967 km² respectively. The latter, however, declined by 29.2% since 1990. On a habitat level, it was most often observed in primary forest habitats of different degradation stages (85.7%, n = 21). The fundamental niche of A. trichotis is most likely restricted by climatic factors. Although it can be found in moderately degraded forests, it is known to depend on the availability of tree holes and therefore old-growth forest structures. Ongoing deforestation and habitat fragmentation are likely to be the major threats to the survival of this species. Our ENMs provide evidence on where to intensify survey efforts on the elusive Hairy-eared Dwarf Lemurs of Madagascar.

Spacing and Mate Attraction: Sex-Specific Function of Advertisement Calls in the Northern Giant Mouse Lemur (Mirza zaza).

It has been proposed that primates use advertisement calls exclusively to negotiate spacing, but the function of female calls has rarely been studied. Here, we investigated the function of male and female advertisement calls in the northern giant mouse lemur (Mirza zaza),a non-gregarious nocturnal primate from north-western Madagascar. We recorded advertisement calls and associated behaviours of 35 M. zaza individuals at the Duke University Lemur Center. We found that females of M. zazaexclusively use their advertisement calls to advertise oestrus. In contrast, male advertisement calls appeared to be used in a spacing context. These findings show that primates can use their advertisement calls for both spacing and mate attraction, and that the sexes may differ in how they use these calls. The novel find of females of M. zazaattracting mates with loud advertisement calls contrasts with many non-primate taxa, where acoustic mate attraction is usually a function of male advertisement calls, and with other primates, where females use visual and olfactory cues to attract males. The loud female advertisement calls of M. zaza likely ensure mating success during the short receptive phase in this non-gregariously foraging, nocturnal primate.

Range Extension and Behavioural Observations of the Recently Described Sheth's Dwarf Lemur (Cheirogaleus shethi).

Sheth's dwarf lemur, Cheirogaleus shethi, is a small, recently discovered nocturnal primate endemic to northern Madagascar. Unlike many other nocturnal lemurs, C. shethi lives sympatrically with morphologically similar species of its cryptic genus, making it difficult for biologists to determine its population density and distribution. Here, we present new data and observations of this species. During a series of rapid biodiversity assessments in the SAVA region of north-eastern Madagascar, we observed C. shethi in 10 different sites, 9 of which were not previously known to harbour C. shethi populations. More significantly, 2 of these sites, in Analamanara, were situated approximately 20 km south of the previously known southern extremity of this species' distribution. This represents a large increase in the previously limited geographic range of this species. Moreover, our relatively high encounter rates at these sites suggest that C. shethi population densities may be high. We also observed C. shethi in human-altered (e.g., vanilla plantations) and non-forest, savannah environments, suggesting that this species can tolerate disturbed habitats. Our findings therefore provide important additional information on the distribution of C. shethi populations and highlight the necessity of further study for the conservation of this species.

Forest fragmentation and edge effects impact body condition, fur condition and ectoparasite prevalence in a nocturnal lemur community.

Forest fragmentation and edge effects are two major threats to primate populations. Primates inhabiting fragmented landscapes must survive in a more degraded environment, often with lower food availability compared to continuous forests. Such conditions can have deleterious effects on animal physiological health, yet some primates thrive in these habitats. Here, we assessed how forest fragmentation and associated edge effects impact three different components of physiological health in a nocturnal primate community in the Sahamalaza-Iles Radama National Park, northwest Madagascar. Over two periods, 6 March 2019-30 October 2019 and 10 January 2022-17 May 2022, we collected data on body condition, fur condition scores and ectoparasite prevalence for 125 Mirza zaza, 51 Lepilemur sahamalaza, 27 Cheirogaleus medius and 22 Microcebus sambiranensis individuals, and we compared these metrics between core and edge areas of continuous forest and fragmented forest. Body condition scores for all species varied between areas, with a positive response to fragmentation and edge effects observed for M. zaza and L. sahamalaza and a negative response for C. medius and M. sambiranensis. Fur condition scores and ectoparasite prevalence were less variable, although M. zaza and L. sahamalaza had a significantly negative response to fragmentation and edge effects for these two variables. Interestingly, the impacts of fragmentation and edge effects on physiological health were variable-specific. Our results suggest that lemur physiological responses to fragmentation and edge effects are species-specific, and body condition, fur condition and ectoparasite prevalence are impacted in different ways between species. As other ecological factors, including food availability and inter/intraspecific competition, likely also influence physiological health, additional work is required to determine why certain aspects of lemur physiology are affected by environmental stressors while others remain unaffected. Although many nocturnal lemurs demonstrate resilience to fragmented and degraded habitats, urgent conservation action is needed to safeguard the survival of their forest habitats.

Morphological variability or inter-observer bias? A methodological toolkit to improve data quality of multi-researcher datasets for the analysis of morphological variation.

OBJECTIVES: The investigation of morphological variation in animals is widely used in taxonomy, ecology, and evolution. Using large datasets for meta-analyses has dramatically increased, raising concerns about dataset compatibilities and biases introduced by contributions of multiple researchers. MATERIALS AND METHODS: We compiled morphological data on 13 variables for 3073 individual mouse lemurs (Cheirogaleidae, Microcebus spp.) from 25 taxa and 153 different sampling locations, measured by 48 different researchers. We introduced and applied a filtering pipeline and quantified improvements in data quality (Shapiro-Francia statistic, skewness, and excess kurtosis). The filtered dataset was then used to test for genus-wide sexual size dimorphism and the applicability of Rensch's, Allen's, and Bergmann's rules. RESULTS: Our pipeline reduced inter-observer bias (i.e., increased normality of data distributions). Inter-observer reliability of measurements was notably variable, highlighting the need to reduce data collection biases. Although subtle, we found a consistent pattern of sexual size dimorphism across Microcebus, with females being the larger (but not heavier) sex. Sexual size dimorphism was isometric, providing no support for Rensch's rule. Variations in tail length but not in ear size were consistent with the predictions of Allen's rule. Body mass and length followed a pattern contrary to predictions of Bergmann's rule. DISCUSSION: We highlighted the usefulness of large multi-researcher datasets for testing ecological hypotheses after correcting for inter-observer biases. Using genus-wide tests, we outlined generalizable patterns of morphological variability across all mouse lemurs. This new methodological toolkit aims to facilitate future large-scale morphological comparisons for a wide range of taxa and applications.

Environmental drivers of Cheirogaleidae population density: Remarkable resilience of Madagascar's smallest lemurs to habitat degradation.

AIM: Global animal populations are in decline due to destruction and degradation of their natural habitat. Understanding the factors that determine the distribution and density of threatened animal populations is therefore now a crucial component of their study and conservation. The Cheirogaleidae are a diverse family of small-bodied, nocturnal lemurs that are widespread throughout the forests of Madagascar. However, many cheirogaleid lemurs are now highly threatened with extinction and the environmental factors that determine their distribution and population density are still little known. Here, I investigated the environmental drivers of Cheirogaleidae population density at genus level. LOCATION: Various forest sites across Madagascar. METHODS: I investigated how six environmental variables affect Cheirogaleidae population density at the genus level via random-effect meta-analyses. I then used a generalized linear mixed-effects model to identify the primary predictors of Cheirogaleidae population density. Finally, I investigated how the population density of this family of lemurs varies between protected and unprotected areas of Madagascar via a GLM analysis. RESULTS: My results indicate that the relationships between the tested environmental factors and population density are genus-specific among the Cheirogaleidae. Rather remarkably, the density of Microcebus appears to have a profoundly positive relationship with anthropogenic disturbance and a negative relationship with forest cover, a finding that is also reflected by larger population densities within unprotected areas in comparison with localities within Madagascar's protected area network. MAIN CONCLUSIONS: The results of this study are highly encouraging for the conservation of the Cheirogaleidae and highlight the remarkable resilience of these lemurs to habitat degradation and anthropogenic activity. However, this study also outlines the dearth of knowledge that we have for many species, and why these data are urgently needed to understand the biogeography and ecology of threatened animal populations and implement successful conservation.