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Dickinson J.L.,Cornell University | Ferree E.D.,Keck Science Center | Stern C.A.,Cornell University | Swift R.,Cornell University | Zuckerberg B.,University of Wisconsin - Madison
Behavioral Ecology | Year: 2014

Delayed and localized dispersal are fundamental life-history traits associated with formation of family groups and kin neighborhoods. Although the field has focused mainly on resource benefits and ecological constraints as drivers of delayed dispersal, social benefits of nepotism can also be important. Resources and nepotism are theoretically correlated as the affordability of nepotism scales with resource abundance. Rarely have both been analyzed simultaneously within a single analysis. Western bluebird sons (Sialia mexicana) stay in family groups on mistletoe-based territories for winter, disperse locally to form kin neighborhoods in spring, and have a low level of facultative helping by sons, brothers, and grandsons. Although a son's tendency to remain on the natal territory increased with the number of parents present, mistletoe volume on the natal territory was a good predictor of sons staying home only for groups where the mother alone was present. Overwinter survival of sons was exceptionally high (95%) such that neither resources nor parental presence predicted survival advantages during the first year of life. When sons stayed on their natal territory for winter, their spring presence increased with the volume of mistletoe on their winter territory and was higher if they wintered with at least 1 parent. Stay-at-home sons acquired a portion of their parents' territory in spring, including mistletoe that scaled with their parents' mistletoe wealth. Our results indicate that although resources are undoubtedly important for the maintenance of family ties, the importance of maintaining connections with parents is underappreciated in studies of cooperative breeding. © 2014 The Author.

Wurster C.M.,James Cook University | Mcfarlane D.A.,Keck Science Center | Bird M.I.,James Cook University | Ascough P.,Scottish Enterprise | Athfield N.B.,Institute of Geological & Nuclear Sciences
Journal of Cave and Karst Studies | Year: 2010

We investigated the utility of subfossil bat guano as a paleoenvironmental archive by comparing elemental ratios and δ13C, δ15N, and dD values of various simple extracts from bulk material. Solvent-extracted guano yielded consistent C:N and N:H ratios, and δ13C values of solvent-extracted guano exhibited strong covariation with δD values, as well as with the δ13C values of other simple extracts (bulk guano, bulk lipid). The results suggest that reliable records are easily recovered for δ 13C, and also indicate that δ15N values may have utility as a paleoenvironmental archive. Despite coeval d13C values of bulk guano and solvent-extracted guano, 14C ages of the different fractions did not always yield similar ages, indicating that future refinement of a suitable extraction protocol is required. Applying these protocols to an ancient bat guano deposit allowed us to infer that climate at the Grand Canyon during the late Pleistocene was more variable and generally cooler and wetter, relative to Holocene climate. We conclude that guano deposits are an underutilized, yet powerful continental paleoenvironmental archive of climate change for semi-arid and tropical regions.

Lundberg J.,Carleton University | McFarlane D.A.,Keck Science Center
Special Paper of the Geological Society of America | Year: 2016

Significant impacts on cave microclimate from large populations of the bat Rousettus aegyptiacus have been documented in three simple caves in pyroclastic rock of Mount Elgon National Park, Kenya, one of which, Kitum Cave, with few bats, acts as a control, indicating microclimatic variations in the absence of significant biological activity. Seven days of temperature logger records, and on-site mapping of rock and air temperature, humidity, and air flow provide the basis for modeling of heat, water, and CO2 production and dispersion. Internal temperatures in the presence of bats in Mackingeny Cave and Ngwarisha Cave rise to ∼18 °C above ambient (from ∼12 °C to ∼30 °C), but in the control site by only ∼2 °C. Excess bat-generated energy is dissipated by conduction to rock and by ongoing air circulation, the strongest of which accompanies bat entry and exit flights. In Kitum Cave, temperatures that are substantially lower than bat thermo-neutral zone raise concern for Allee effects on long-Term colony fitness: Modeling indicates that a population of at least 100,000 bats should promote colony vitality. Metabolic outputs were modeled to yield corrosional potential: At these population densities, were the caves in limestone, rates of surface denudation caused directly by metabolic outputs would be 1 m in ∼80,000 yr. These results confirm that tropical bats can be effective niche constructionists, by optimizing microclimatic roost conditions, by longer-Term bioerosional optimization of rock surfaces for roosting, and by long-Term niche engineering through zoo-speleogenetic enlargement of roost volume. © 2015 The Geological Society of America. All rights reserved.

Dickinson J.L.,Cornell University | Akcay C.,Virginia Polytechnic Institute and State University | Ferree E.,Keck Science Center | Stern C.,Santa Fe Institute
Behavioral Ecology | Year: 2016

When animals live near family members, this creates potential for incest and inbreeding depression, especially with unfamiliar kin. We examined incest avoidance when birds paired in kin groups and after dispersal in western bluebirds, Sialia mexicana, a cooperative breeder with a persistent, but low frequency of adult males helping at the nest. During their first winter, sons usually live in family groups comprised of parents, brothers, immigrant females, and more rarely, immigrant males and philopatric sisters. Sons usually pair with females that have joined their winter group, although some pair with females they encounter after dispersal. Incestuous pairing among relatives with relatedness ≥0.25 rarely occurred in either context, even considering extrapair fertilizations and other sources of unfamiliar kin. Sons pairing in their winter groups preferentially mated with immigrant females and actively avoided pairing with relatives. After dispersal into kin neighborhoods in spring, active incest avoidance was still required to explain low levels of incest with females within 600 m (2-3 territories) of where sons first bred, whereas absence of incest over larger distances could be explained by random mating. The probability of encountering a female relative within 600 m of where a male settled declined rapidly with dispersal distance to near zero for males dispersing 2 km from home. Although recognition is required to avoid incest when pairing in winter groups or settling near home, female-biased dispersal reduces likelihood of incest to near zero, even when males disperse relatively short distances (e.g., 2 km) from where they were born. © 2016 The Author.

McFarlane D.A.,Keck Science Center | Rentergem G.V.,NA c9 3803919 | Ruina A.,Keck Science Center | Lundberg J.,Carleton University | Christenson K.,2026 Peach Orchard Drive Apt. 23
Acta Chiropterologica | Year: 2015

The Gomantong cave system, Kinabatangan, Sabah (Malaysia) hosts one of the largest bat colonies known from north Borneo. The nightly exodus of Chaerophon plicatus from this site is an economically valuable tourist attraction, and must impose significant controls on the regional ecology. Monitoring ecosystem health requires monitoring bat population size, but no quantitative assessments for the Gomantong colony are available in the literature. Traditional censusing techniques (based on packing density and roost area or on roost exodus counts) yield notoriously unreliable results. Here we have applied innovative image analysis and counting techniques to videographic, photographic and terrestrial laser scanning data obtained in July 2012. The colony exits in a consistent stream along a narrow exit trajectory. The laser scanning of the large cave entrance allowed precise measurement of bat position. Video data provided 0.02-second time resolution. Average flight speed was calculated (10.38 ± 0.85 m/sec), bat exit rate was estimated at three minute intervals (peaking at 14,000 bats/minute) and then summed over the 40 minutes of bat flight. The resultant colony size estimate of 275,625-276,939 (95% confidence interval) individuals of C. plicatus in Gomantong Caves in 2012 demonstrates that the technique is viable, provides a realistic basis for ecosystem management, and can be repeated to monitor ecosystem change. The estimated insect consumption by the colony of this size is 927 ± 191 metric tons of insects per year over an estimated 270 km2 area, a very important component in maintaining ecosystem stability in the Gomantong Forest Reserve and the Kinabatangan Wildlife Sanctuary, as well as pest control over the large agricultural tracts of the region. © Museum and Institute of Zoology PAS.

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