• Assessing grey squirrel dispersal patterns within the landscape using sequence variation

      Stevenson, Claire D.; Ramsey, Andrew; Nevin, Owen T.; Sinclair, William; University of Cumbria (2012)
      The grey squirrel Sciurus carolinensis is thought to have contributed to the decline of red squirrel S. vulgaris populations in the UK through resource competition and disease spread. This study used mtDNA sequencing to assess patterns of grey squirrel dispersal in the UK. Patterns of genetic variation within the dloop sequence were characterised for seven grey squirrel populations. Infiltration directions and potential barriers to dispersal are identified and discussed, with a focus on Cumbria, a county at the forefront of grey squirrel expansion. Understanding the dynamics of grey squirrel dispersal will aid their management at a landscape scale and enhance the conservation of red squirrels.
    • Children of divorce: effects of adult replacements on previous offspring in Argentinean owl monkeys

      Huck, Maren; Fernández-Duque, Eduardo; University of Pennsylvania; Centro de Ecologia Aplicada del Litoral, CONICET (Springer, 2012)
      According to the Evolutionary Theory of the Family, the replacement of one pair-member by an intruder may have profound consequences for the existing offspring. Step-parents are expected to provide less care towards unrelated immatures than to genetic offspring, unless caring also serves as a mating strategy. Furthermore, because an intruder will be a potential mate for opposite-sexed offspring, relationships between offspring and same-sex parents are predicted to deteriorate. To test these predictions, we studied an Azara’s owl monkey (Aotus azarai) population in Argentina exhibiting serial monogamy and biparental care. Since 1997, we have collected demographic data from ca. 25 groups and inter-individual distance data from ca. 150 marked individuals. First, we compared survival and dispersal age of immatures in groups with and without replacements to investigate whether parental care serves as a mating strategy. Second, we compared sexspecific age at dispersal for groups with replacement of opposite-sex parents, same-sex parents, or in stable groups in order to test whether relationships between offspring and same-sex parents deteriorated after the replacement of the other parent. Survival and dispersal ages were not negatively associated with replacements, suggesting that male care might serve, at least partly, as a mating strategy. The time lag between a replacement and the subsequent dispersal of female offspring was greater if the intruder was a male, while the offspring and same-sex parents were less often nearest neighbors after replacements than before. Our results suggest that family disruption through the replacement of a parent is not associated with decreased offspring survival or early dispersion of juveniles, but deteriorates parent–offspring relationships.
    • The floater's dilemma: use of space by wild solitary Azara's owl monkeys, Aotus azarae , in relation to group ranges

      Huck, Maren; Fernández-Duque, Eduardo; University of Derby; Yale University (Elsevier, 2017-03-26)
      The fate and behaviour of animals that leave their natal group (‘floaters’) is usually poorly understood, which can limit the understanding of a species' population dynamics. Attempted immigrations can have serious negative effects on residents who therefore may forcibly reject intruders. Consequently, floaters face a dilemma: they need to leave their natal range to find a breeding territory while trying to avoid potentially lethal rejections from established groups. To examine the hypothesis that floating Azara's owl monkeys avoid established groups temporally, we compared time-matched locations of floaters and groups with randomly selected distances. To examine the hypothesis that floaters avoid established groups spatially, we compared the utilization distribution overlap indices (UDOIs) for core areas of floaters and groups with randomly expected UDOIs. Based on average home range sizes and areas of overlap between floaters, we estimated the floater density in the study area to be 0.2e0.5 per group. The temporal avoidance hypothesis was not supported, since time-matched distances were smaller than distances of random locations, and not larger as predicted under this hypothesis. The spatial avoidance hypothesis, in contrast, was supported, with smaller UDOIs for core ranges than predicted. In conclusion, solitary owl monkeys seem to solve the floater's dilemma by trying to stay in relatively close proximity to groups while still avoiding their core ranges. Floaters thus maximize the number of groups with which they have contact, while being able to leave a group's territory quickly if detected by residents. While no marked sex differences in patterns were detected, there was a strong stochastic element to the number of floaters of a particular sex, thus resulting in a locally uneven operational sex ratio. This, in turn, can have important consequences for various aspects of the population dynamics.
    • Home-range use of wild solitary Azara's owl monkeys (Aotus azarae) in relation to group ranges in Formosa, Argentina

      Huck, Maren; Fernández-Duque, Eduardo; University of Derby (International Primatological Society, 2016-08-25)
      Little is known about the secret lives of subadult owl monkeys that have left their natal group to "float" in the population, before they find a new group or die. Groups are territorial, and in suitable habitat territories take up all available space. Thus, “floaters” cannot avoid overlapping with established groups while roaming, and may be attacked by groups that are trying to avoid take-overs. We hypothesized that floaters minimize temporal and/or spatial overlap with groups. Using location data of 23 floaters and surrounding groups (range 23-96 (25-973), median=42 (93) locations for floaters (groups)), we determined home-range sizes and home-range overlaps. Temporal avoidance was analyzed by comparing floaters’ distances to groups during simultaneous observations to distances between randomly selected location pairs of floaters and groups. Spatial avoidance was investigated by comparing the actual Utilization Distribution Overlap Indices (UDOIs) for 50% kernels of floaters and groups against UDOIs derived from randomized home-ranges. We predicted greater distances for parallel observations and lower spatial/home range overlap. Linear mixed models did not suggest temporal avoidance (parallel=361.8m vs. 381.5m), but UDOIs were smaller than expected based on randomized ranges (0.012 vs. 0.014). It seems that floaters do not monitor exact locations of groups closely enough to avoid them completely, but preferentially use areas outside the core home range of groups. Funding to EFD: NSF-BCS-0621020/1219368/1232349, NSF-REU 0837921/0924352/1026991 and NIA- P30 AG012836-19
    • Migration

      Huck, Maren; University of Derby; University of Derby; United Kingdom (Wiley, 2017-04)
      Primate societies are not static. Group composition changes due to births and deaths, and also by emigration and immigration of individuals between different groups. These transfers, while considered costly for the individual, have important implications for the individual itself and the population as a whole. While, generally speaking, dispersal is male-biased in strepsirrhine and catarrhine primates and female-biased in platyrrhines, variations even between different populations of the same species become increasingly apparent. This indicates that dispersal is a conditional strategy that depends on numerous external and internal proximate factors, as well as individual cost–benefit calculations. Although the advent of more advanced molecular techniques has started to provide more insights into dispersal patterns, the life of dispersing floaters remains a challenging topic, but is fundamental in order to not only understand the general behavioral ecology and evolution of a species but also help evaluate the viability of populations.
    • Spatio-genetic population structure in mustached tamarins,Saguinus mystax

      Huck, Maren; Roos, Christian; Heymann, Eckhard W.; Abteilung für Verhaltensökologie & Soziobiologie, Deutsches Primatenzentrum; Gene Bank of Primates, FG Primatengenetik, Deutsches Primatenzentrum (2007)
      Dispersal and philopatry influence gene flow and thus the spatio-genetic structure within and between populations. In callitrichids the flexible social and mating system corresponds with a variable migration pattern where both sexes might be philopatric or might disperse. We investigated the relationship between the spatiogenetic structure and migration patterns in a population of mustached tamarins, Saguinus mystax. Using the rapidly evolving hypervariable region I (HVI) of the mitochondrial control region and 11 microsatellite markers we detected a high variation (HVI: 16 haplotypes in 69 individuals; microsatellites: HO ¼ 0.75, average: 7.45 alleles/locus), with mating partners usually not sharing the same haplotype, indicating that matings are generally between partners that are not closely related. Similar high variance of haplotype differences for male-male and female-female pairs, along with a slightly higher number of haplotype differences in males show that both sexes habitually migrate. Spatial analyses suggest that females usually migrate longer distances, corresponding to very limited breeding positions for females in a polyandrous social mating system.
    • Using GPS telemetry to validate least-cost modeling of gray squirrel ( Sciurus carolinensis) movement within a fragmented landscape

      Stevenson, Claire D.; Ferryman, Mark; Nevin, Owen T.; Ramsey, Andrew; Bailey, Sallie; Watts, Kevin; University of Cumbria; Forest Research UK (Wiley, 2013)
      In Britain, the population of native red squirrels Sciurus vulgaris has suffered population declines and local extinctions. Interspecific resource competition and disease spread by the invasive gray squirrel Sciurus carolinensis are the main factors behind the decline. Gray squirrels have adapted to the British landscape so efficiently that they are widely distributed. Knowledge on how gray squirrels are using the landscape matrix and being able to predict their movements will aid management. This study is the first to use global positioning system (GPS) collars on wild gray squirrels to accurately record movements and land cover use within the landscape matrix. This data were used to validate Geographical Information System (GIS) least-cost model predictions of movements and provided much needed information on gray squirrel movement pathways and network use. Buffered least-cost paths and least-cost corridors provide predictions of the most probable movements through the landscape and are seen to perform better than the more expansive least-cost networks which include all possible movements. Applying the knowledge and methodologies gained to current gray squirrel expansion areas, such as Scotland and in Italy, will aid in the prediction of potential movement areas and therefore management of the invasive gray squirrel. The methodologies presented in this study could potentially be used in any landscape and on numerous species.