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A grumpy female rufous mouse captured during the fieldwork expedition. This is one of the collared individuals of this study. Photo credit: Veronarindra Ramananjato
Source publication
Finding sleeping sites is important for the fitness of many mammal species. Like most nonhuman primates, Madagascar's mouse lemurs (genus: Microcebus) are thought to exclusively use arboreal sleeping sites. The rufous mouse lemurs (Microcebus rufus) in Ranomafana National Park (southeastern Madagascar) have always been documented to sleep in either...
Citations
... Lemurs, endemic to the island nation of Madagascar, are in decline, with extinction threatening 87% of species (Estrada et al., 2017). Arboreal lemur species occasionally come to the ground for foraging (Eppley et al., 2016a), sleeping (Eppley et al., 2016b;Ramananjato et al., 2022), and hibernation (Blanco et al., 2013). While a few studies suggested that predation risk influences lemur terrestriality (LaFleur et al., 2014), none to our knowledge have investigated how direct predator presence influences their ground use. ...
It is thought arboreal species avoid foraging on the ground due to perceived predation risk, making the study of when and where arboreal species use the ground key in understanding foraging versus safety tradeoffs. We used publicly available, opportunistic, camera-trap observations from surveys across Madagascar to examine whether arboreal lemur ground use was spatially and temporally related to fosa (Cryptoprocta ferox), a native predator, and human presence. We observed 14 species of diurnal lemur (n = 287 individual observations) and six species of nocturnal lemur (n = 105 individual observations). With static two-species occupancy models and kernel density estimation, we found diurnal and nocturnal lemur ground use was spatially and temporally related to fosa presence. Diurnal lemurs used the ground less at camera locations where fosa were present compared to camera locations where they were absent, particularly if those camera locations lacked other native carnivores. Nocturnal lemurs used the ground more at camera locations fosa were observed at within the past 5 days compared with camera locations where fosa were not observed at within the past 5 days. Despite humans and diurnal lemurs being active at the same time 80% of the diel cycle (temporal overlap Δ = 0.80; 95% confidence interval [CI]: 0.75–0.85), diurnal lemur spatial or temporal use of the ground and human presence were unrelated. Diurnal lemur temporal overlap with humans at camera locations where fosa were uncommon was higher (Δ = 0.79; 95% CI: 0.71–0.86) compared with where fosa were common (Δ = 0.57; 95% CI: 0.46–0.66). Future research on how arboreal lemurs navigate ground use in a multipredator landscape should include behavioral observations to better understand animal decision-making.
... griseorufus, Génin, 2008; M. lehilahytsara, Randrianambinina et al., 2003 M. ravelobensis, Thorén et al., 2011;M. rufus, Atsalis, 1999, Ramananjato et al., 2022 can cope with thermoregulatory challenges under low temperatures using torpor or even hibernation (Blanco et al., 2018;Salewski & Watt, 2016). This may help to explain why more than 78% of the variation in body mass and body length could not be explained by climatic factors. ...
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.
Current incessant threats of environmental changes, such as habitat fragmentation, may disrupt vital mutualistic plant-frugivore networks, threatening the whole ecosystem. To advance our knowledge of the magnitude of the impacts of such disruption, we need a better understanding of its structure and robustness. We addressed this by comparing several aspects of plant-frugivore networks in the forest edge and interior habitats of a fragmented forest, using field data on fruit removal by a community of frugivorous birds and lemurs from 40 tree species over 30 months. While the plant-frugivore networks in both habitats were significantly less nested than random expectations, the network in the forest edge habitat had higher value of nestedness compared to the network in the forest interior. Also, the networks in both habitats were highly modular compared to random expectations, with a dominance of species that are highly interactive within its modules. We also found that fruit size, weight, and color as well as tree height predicted the structural role of plants in the networks and their degree of specialization. Finally, the removal/loss of best-connected plants or animals resulted in a weak robustness of the networks in both habitats; this vulnerable pattern is more pronounced in forest edges than interior habitats. Interestingly, the loss of large-bodied seed dispersers from either habitat did not affect much the robustness of the networks; in contrast, when small-sized species were eliminated first, the network became less robust, especially for the edge community. These findings highlight the need to preserve species interactions in forest edges to avoid the collapse of the network, mitigating the impacts of species extinctions on ecosystem equilibrium.
