Ateles Hybridus) in a Fragmented Forest in Northern Colombia

Universidad de los Andes – Carolina Urbina–Tesis de grado para obtener el título de bióloga – Director: Andrés Link–Sustentada 26 de Junio de 2014 Ranging patterns of brown spider monkeys (Ateles hybridus) in a fragmented forest in northern Colombia Key words: Levy pattern, Ateles hybridus, power law distribution, turning angle, step lenght Abstract Recent studies on wild spider monkeys have described that their ranging and foraging patterns resemble what is best known in physics as levy-walk patterns. Here we analyzed the ranging patterns of brown spider monkeys (Ateles hybridus) in a small forest fragment using maximum likelihood methods for adjusting power law distributions to step length and resting period times. Daily paths were analyzed using the CPT (change points detection test). Our results suggest that spider monkeys living in a small fragmented forest do not follow Levy walk patterns and that their ranging and foraging strategies seem to be more goal-oriented. As proposed for other primates, spider monkeys may adjust their ranging behavior to restrictive situations such as habitat fragmentation. Thus, under this scenario spider monkeys may modify their ranging strategies, and this may differ from the results obtained in studies conducted in continuous forests. Thus, we suggest forest fragmentation restricts spider monkey´s movement patterns as well as male and female use of their territories. Introduction A large number of recent studies have provided consequences of habitat fragmentation on the evidence on the direct and indirect impacts of behavioral ecology of primates. habitat fragmentation on primate populations and wildlife (Aggimarangsee, 2013). Habitat The brown spider monkey (Ateles hybridus) is fragmentation has four major effects: [I] direct considered to be Critically Endangered (CR) and facing a relatively high risk of extinction (IUCN, decrease on the available habitat, [II] increase in the number of habitat patches, [III] decrease in 2008). It has been included on the 25 most habitat patch size, and [IV] increase in patch endangered species of primates and in need of attention for conservation and research isolation (Fahrig, 2003). As the ecosystems where primates currently live are transformed by (Mittermeier et al., 2012). The slow life history anthropogenic activities, species also adapt and variables of brown spider monkeys limit their potential flexibility to adapt to habitat loss and modify the way they use their habitat and exploit the available resources. For example, recent fragmentation. Spider monkeys have extremely studies have found that in smaller fragments, long reproductive cycles; are large-bodied ripe fruit specialists and need large areas to obtain primates travel shorter daily distances, revisit feeding trees more often, and use the forest in a resources for their survival and reproduction (Link more uniform manner (Boyle et al, 2013). et al., 2010). For these primates, an efficient foraging strategy is vital to the survival, especially Although there are several long-term studies on the dynamics of fragmented forests like “The in fragmented forests. The Levy-walk is known as Biological Dynamics of Forest Fragments Project” an efficient foraging strategy during searching for new resources. A Levy-walk is a type of random in Brazil (Boyle et al., 2013), and “Los Tuxtlas” in Mexico (Crtistobal-Azkárate et al., 2013), there is walk in which step lengths are drawn by a power still a gap in our knowledge on the effects and law distribution and turning angles are shaped by a uniform distribution (James et al., 2011). A power law distribution has the general form p(x) use CPT test to detect places where Ateles ~ x -α where α is a constant parameter of the hybridus change the direction within their daily distribution known as the scaling parameter. The paths and to examine whether these points are scaling parameter typically lies in the range related to the visitation of key feeding resources. 2 < α ≤ 3 although there are occasional exceptions These results are then discussed towards better (James et al, 2011). The power law applies only understanding which ecological aspects of habitat for values greater than some minimum xmin. In fragmentation alter spider monkeys movement such cases it is said that the tail of the distribution and foraging patterns. follows a power law (Clauset et al., 2009). The foraging strategies of Ateles geoffroyi have been Methods suggested to follow Levy walk patters, and this is Study site and animals reflected in the power law distribution of their Data were collected at the Hacienda San Juan de steps which had a scaling parameter of 2.18 and Carare (06 ° 43 'N, 74 ° 09' W), located near the the distributions of rest intervals with exponent of Magdalena river, within the department of 1.7 (Ramos-Fernandez et al., 2004). Santander in Colombia. The study site is within a The Levy hypothesis does not consider the seasonally flooded forest of roughly 65 ha and cognitive ability of individual foragers, and several fragmented about eight years ago due to selective studies have suggested memory can be a logging and the opening of pastures for cattle determinant factor in an efficient foraging ranching. It is comprised by a thin forest fragment strategy of spider monkeys (Di Fiore & Suares, of riverine forest where four species of primates 2007). Even when food patches are common, live: the brown spider monkey (Ateles hybridus), primates might rely on spatial memory to travel to red howler monkeys (Alouatta seniculus), white- highly productive or preferred resources, rejecting fronted capuchins (Cebus albifrons) and night less productive but closer resources (Cunningham monkeys (Aotus griseimembra) (Link et al., 2010). & Janson, 2007). Trying to investigate the spatial Two groups of A. hybridus were habituated to mental representation of primates has multiple researchers since 2007 and studied continuously limitations. The most common observation is that thereafter. Data analyzed for this study comes the paths used by primates when foraging among from two social groups: SJ1 (six females and five spatially fixed resources often appear to be goal- males) and SJ2 (five females and three males). oriented. In nearly all cases, routes taken between known resources are approximate to straight lines Data Collection (Janson & Byrne, 2007). Byrne et al., 2009 Data were collected from January 2010 to designed the (CPT) test, which serves to test December 2012. All monkeys were recognized by hypothesis associated with goal oriented paths. facial markings and unique anatomical This test examines paths composed of short linear characteristics. We conducted behavioral follows segments (vectors) to detect points at which the from dawn to dusk (when possible) and collected direction of these vectors changes significantly, data using focal animal sampling (Altmann 1974). that is, ‘change-points’ in otherwise more uniform The behavior of the focal subject was recorded at or undirected travel (Asensio et al, 2011). five minute point records. The spatial position was recorded every 15 minutes based on The main goal of this study is to characterize the georeferenced landmarks set at 25m intervals movement patterns of Ateles hybridus in a along the project´s trail system and over 2000 fragmented forest and identify which aspects of feeding trees. All feeding events were registered, the path differ with respect to those reported for taking note of the plant species eaten, the item spider monkeys living in continuous forests. We 2 consumed (e.g., fruits, flowers, etc.), the location were obtained by calculating the angles of the event, and the beginning and ending time associated with two consecutive vectors. A of each feeding bout. frequency distribution of the angles of rotation was produced with intervals size of 10 °. Data analysis All statistical analysis was performed using R Travel change-point detection 3.1.1. The probability distributions fit was The change point detection test (CPT) was created performed with a maximum likelihood method by Byrne et al (2009); and was used to reliably and the Kolmogorov Smirnov goodness of fit test determine the points on which there was a (Clauset et al.,2009). Figures were created with significant change in the direction of the path of Arcgis 10.2 and R 3.1.1. monkeys. CPT examines paths composed of short segments (vectors) for detecting points at which Ranging -walk- patterns the direction of these vectors change. This test The trajectories of individual spider monkeys were has a parameter q, which must be fixed for every analyzed according to the methods used by species. The test was performed 2940 times for Ramos-Fernandez et al. (2004) and Turching 490 paths and different values of q oscillating (1998). The path of each focal animal consists of a between 1 and 6 with an alpha value of 0.05. We sequence of Cartesian coordinate pairs, one pair found that the CPT was most sensitive at q = 5. for each 15-min interval. A step was taken as an interval in which one or both of the coordinates in Finally, we performed a Wilcoxon paired test to two consecutive samples differ. The length of make a comparison between the location of each step was calculated as the Euclidean change points and points of nutritional distance between the positions in two importance, (a point of nutritional importance is consecutive samples. In some cases, observers classified as such if the specie of feeding lost sight of the focal animals; steps were not represented 10% or more of the total nutriment calculated for these intervals. Only consecutive consumed in the whole day) these points were routes lasting >6.5 hours of focal animal follows also compared with random locations (a pair of were included in the analysis. The frequency coordinates resulting from a random drawing distribution of step lengths was analyzed using a from all points of the route analyzed ) and with range of 10 meters.

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