Population assessment and habitat associations of the Visayan Hornbill(Penelopides panini)in Northwest Panay,Philippines

Background:Seven out of ten hornbill species in the Philippines are threatened with extinction.Among these is the endangered Visayan Hornbill(Penelopides panini),found on the islands of Panay and Negros.Threatened by habitat loss and hunting,its population size is thought to have declined from 1800 individuals 20 years ago to less than 1000.However,a recent study on Negros estimated 3564 individuals across three core forest blocks.This study aims to quantify the Visayan Hornbill population size in and around the Northwest Panay Peninsula Natural Park(NWPPNP)on Panay,the largest contiguous low-elevation forest landscape remaining across its range,and its broad habitat associations across a gradient of environmental degradation.Methods:Hornbills were surveyed using 10-min distance sampling point counts(n=367)along transects(average length 1.1 km).Environmental variables were recorded along transects,while habitat was classified into primary forest,secondary forest,plantation,or open habitat.Distance software was used to estimate population densities stratified by habitat,with the overall population estimate taken as a mean of habitat density estimates weighted by habitat area.Using generalized linear mixed models,hornbill occurrence was modelled using combinations of nine environmental variables as main and two-way fixed effects.Results:Surveys covered 204.4 km^(2) of the 374.8 km^(2) Northwest Panay Peninsula.Hornbills were not recorded in plantations or open habitats.Hornbill density was significantly higher in primary forest(17.8 individuals/km~2±26.9%CV)than in secondary forest(3.7 individuals/km^(2)±33.2%CV;z=15.212,P<0.001).The overall population estimate for the NWPPNP and environs is 2109 individuals,and 2673 individuals for the entire Northwest Panay Peninsula.Hornbill presence was best explained by a model including distance from the Park boundary alongside five interaction effects and transect as a random effect.Distance,and the interaction between distance and medium-sized trees were significant predictors of hornbill presence.Conclusions:Our study evidences the habitat preference of the Visayan Hornbill,highlights the importance of the NWPPNP for the species'conservation,and provides strong evidence for re-assessing the global population size.

Predictors of dominance rank and agonistic interactions in captive Livingstone's fruit bats

Male dominance hierarchies have been studied in many animals but rarely in bats(Chiroptera).The dominance rank of social animals may dictate access to resources and mates;therefore,it has important implications for an individual's fitness and is crucial for successful captive man-agement.Between January and December 2018,at both Bristoi Zoo Gardens(Bristol,UK)and Jersey Zoo(Jersey,British Isles),we observed 19 male Livingstone's fruit bats Pteropus livingstonii using focal follows for 345 h overall,noting the outcome of all agonistic interactions.We recorded instigators of interactions,along with winners and losers,and analyzed these data using the R-package"EloRating"to create Elo-rating temporal plots of dominance ranks.We used generalized linear mixed models and multiple linear regression to analyze interaction data and test hypotheses regarding predictors of dominance rank,frequency of agonistic interaction,and choice of interaction partner.Age was positively correlated with dominance rank up to around year 9,when an asymptote was attained.Highly ranked bats instigated the most agonistic interac-tions,and largely directed these interactions at bats with much lower rankings than themselves.Hierarchies were extremely stable throughout the data collection period at both sites.We conclude that Livingstone's fruit bats have a stable linear dominance hierarchy,with high-ranking,typ-ically older males instigating the most interactions with lowest ranking males to secure dominance rank.This study adds to the limited discourse on Pteropus social behaviors,indicating that some bat species may have social systems similar in complexity to some nonhuman primates.