Padrões de movimentação de micos-leões pretos (Leontopithecus chrysopygus) em um fragmento de Mata Atlântica no interior do estado de São Paulo, Brasil
Arquivos
Data
2020-09-03
Autores
Bufalo, Felipe Soares [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Primatas executam diariamente uma série de decisões acerca de quando, para onde e por que se mover. No entanto, pouco sabemos sobre quais são os fatores mais influentes no processo de decisão em primatas e, portanto, responsáveis por moldar rotas diárias, principalmente em pequenos fragmentos. Neste estudo buscamos entender quais aspectos sociais e ambientais influenciaram o processo de planejamento de rotas do frugívoro-insetívoro mico-leão-preto (BLT) em um remanescente de Mata Atlântica de 100 ha. Previmos que os locais de frugivoria seriam o principal fator para o direcionamento de rotas. Ainda, esperávamos que os limites físicos da área fossem fatores importantes para a condução de rotas diárias. Seguimos um grupo de BLT por 42 dias completos entre março e agosto de 2019, totalizando 379,9 horas de observação. Registramos a localização e os comportamentos do grupo através de amostragens de varredura a cada cinco minutos, bem como todos os eventos de alimentação, long calls e encontros entre grupos. Determinamos a distribuição espacial das espécies de frutos e dos locais de frugivoria usados mensalmente através de índices de agregação R, além das distâncias médias entre os indivíduos de cada espécie. Também determinamos, para cada mês, as distâncias médias entre locais aleatórios dentro da área utilizada e locais de frugivoria (empty space distances). Dividimos a área utilizada entre fronteira do território, área central e borda do fragmento e comparamos o uso entre elas. Aplicando o change point test em rotas diárias, identificamos os locais de mudanças significativa de direção, ou change points (CPs), e avaliamos o comportamento grupal associado a cada CP. O grupo utilizou uma área de 46,8 hectares e se deslocou, em média, 1773 m ( 461 m) por dia. Frugivoria e locomoção foram os comportamentos mais frequentes (29,9% e 29,8% das varreduras, respectivamente), seguidos de forrageio com 25,3%. Os encontros entre grupos ocorreram em um a cada 4 dias. Espécies de frutos apresentaram distribuições agrupadas, embora a distância média entre locais de frugivoria seja de 33,4 m ( 22,8 m). Os frutos consumidos com maior frequência corresponderam a plantas densamente distribuídas na área e disponíveis durante a maior parte do estudo, acessíveis, portanto, a curtas distâncias, independentemente do mês e do local. Encontramos um total de 55 CPs. Locomoção foi o comportamento mais frequente associado a CPs (34,54%), seguido de forrageio (25,45%) e frugivoria (12,7%). Embora a variação entre medianas não tenha sido significativa (p = 0,756), encontramos uma maior proporção diária de CPs na fronteira do território (0,021 ± DP 0,05 CPs / pontos de localização), seguida pela borda do fragmento (0,018 ± DP 0,03) e área central (0,008 ± DP 0,01). Nossos resultados indicam que, embora os frutos representem um item importante na dieta de BLTs, locais de frugivoria não parecem direcionar as rotas no fragmento estudado. Por outro lado, estar em um fragmento impõe limites estruturais e possível maior competição intraespecífica, responsáveis por obrigar mudanças de direção e consequentemente explicar maior densidade de CPs próximos às bordas (borda do fragmento e fronteira do território). Em conclusão, enquanto estudos anteriores em áreas maiores apontam locais de alimentação como o principal fator direcionando as trajetórias de primatas, nosso estudo sugere que o processo de planejamento de rotas pode depender do contexto.
In a daily basis, primates execute a wide variety of decisions concerning what, when and where to move. However, our knowledge about what are the most important factors influencing primates’ decision processes and, therefore, shaping daily routes, is still insufficient, particularly in small forest fragments. Here we intended to understand what social and environmental aspects influenced the frugivorous-insectivorous black lion tamarins’ (BLT) daily route planning process in a 100-ha Atlantic Forest remnant. We predicted that fruit feeding sites would be the principal factor driving daily routes. Also, we expected physical limits of the area to be important factors for route directing. We followed a group of BLT for 42 full days between March and August 2019, totaling 379.9 observation hours. We recorded the GPS location and group behaviors through scan sampling every five minutes, as well as all observed feeding events, long calls, and intergroup encounters. We determined the spatial distribution of fruit species and fruit feeding sites used monthly using the aggregation indexes R, and estimated the mean distances between fruit species’ individuals. We also determined the mean distances that BLT should travel from random locations within the home range (i.e., the empty space distances) to reach a fruit feeding site each month. We divided the home range into territory border, central area and fragment edge and tested whether BLT preferred one of these zones. On each daily route, we identified the locations of significant direction changes, called change points (CPs), using the Change Point Test and assessed the group behavior associated to each CP. The group used an area of 46.8 hectares and traveled, on average, 1773 m ( 461 m) daily. Frugivory and locomotion were the most frequent behaviors (29.9% and 29.8% of the scans, respectively), followed by foraging with 25.3% of the scans. Intergroup encounters occurred one every 4 days. Fruit species presented clumped distributions (R < 0), although fruit spots were located, on average, every 33.4 m ( SD 22.8 m). Most frequently consumed fruit resources were plants densely distributed in the area and available during most of the study period, therefore accessible within relatively short distances whatever the moment of the year and the place. We found a total of 55 CPs. Locomotion was the most frequent behavior associated to CPs (34.54%), followed by foraging (25.45%), and frugivory (12.7%). Although the variance of the median was not significant (p = 0.756), we found a higher mean daily proportion of CPs at the territory border (0.021 ± SD 0.05 CPs/location points), followed by fragment edge (0.018 ± SD 0.03) and central area (0.008 ± SD 0.01). Our results indicate that, although fruits represent an important item in BLT’s diet, fruit feeding sites did not seem to drive BLT’s trajectories in the studied fragment. In contrast, being in a fragment imposes structural limits and a possibly higher intra-specific competition. When arriving to these limits, there are no other options than to change directions, which can explain the higher density of CPs close to borders (fragment edge and frontier with other group´s home range). In conclusion, while previous studies in larger areas usually point fixed feeding sites as the main factor shaping primates’ trajectories, our study suggests that the route planning process might be context-dependent.
In a daily basis, primates execute a wide variety of decisions concerning what, when and where to move. However, our knowledge about what are the most important factors influencing primates’ decision processes and, therefore, shaping daily routes, is still insufficient, particularly in small forest fragments. Here we intended to understand what social and environmental aspects influenced the frugivorous-insectivorous black lion tamarins’ (BLT) daily route planning process in a 100-ha Atlantic Forest remnant. We predicted that fruit feeding sites would be the principal factor driving daily routes. Also, we expected physical limits of the area to be important factors for route directing. We followed a group of BLT for 42 full days between March and August 2019, totaling 379.9 observation hours. We recorded the GPS location and group behaviors through scan sampling every five minutes, as well as all observed feeding events, long calls, and intergroup encounters. We determined the spatial distribution of fruit species and fruit feeding sites used monthly using the aggregation indexes R, and estimated the mean distances between fruit species’ individuals. We also determined the mean distances that BLT should travel from random locations within the home range (i.e., the empty space distances) to reach a fruit feeding site each month. We divided the home range into territory border, central area and fragment edge and tested whether BLT preferred one of these zones. On each daily route, we identified the locations of significant direction changes, called change points (CPs), using the Change Point Test and assessed the group behavior associated to each CP. The group used an area of 46.8 hectares and traveled, on average, 1773 m ( 461 m) daily. Frugivory and locomotion were the most frequent behaviors (29.9% and 29.8% of the scans, respectively), followed by foraging with 25.3% of the scans. Intergroup encounters occurred one every 4 days. Fruit species presented clumped distributions (R < 0), although fruit spots were located, on average, every 33.4 m ( SD 22.8 m). Most frequently consumed fruit resources were plants densely distributed in the area and available during most of the study period, therefore accessible within relatively short distances whatever the moment of the year and the place. We found a total of 55 CPs. Locomotion was the most frequent behavior associated to CPs (34.54%), followed by foraging (25.45%), and frugivory (12.7%). Although the variance of the median was not significant (p = 0.756), we found a higher mean daily proportion of CPs at the territory border (0.021 ± SD 0.05 CPs/location points), followed by fragment edge (0.018 ± SD 0.03) and central area (0.008 ± SD 0.01). Our results indicate that, although fruits represent an important item in BLT’s diet, fruit feeding sites did not seem to drive BLT’s trajectories in the studied fragment. In contrast, being in a fragment imposes structural limits and a possibly higher intra-specific competition. When arriving to these limits, there are no other options than to change directions, which can explain the higher density of CPs close to borders (fragment edge and frontier with other group´s home range). In conclusion, while previous studies in larger areas usually point fixed feeding sites as the main factor shaping primates’ trajectories, our study suggests that the route planning process might be context-dependent.
Descrição
Palavras-chave
Leontopithecus chrysopygus, Ecologia do movimento, Change point test, Movement ecology