Browsing by Subject "Animal Migration"

Now showing 1 - 7 of 7
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    Comparing habitat suitability and connectivity modeling methods for conserving pronghorn migrations.
    (PloS one, 2012-01) Poor, Erin E; Loucks, Colby; Jakes, Andrew; Urban, Dean L
    Terrestrial long-distance migrations are declining globally: in North America, nearly 75% have been lost. Yet there has been limited research comparing habitat suitability and connectivity models to identify migration corridors across increasingly fragmented landscapes. Here we use pronghorn (Antilocapra americana) migrations in prairie habitat to compare two types of models that identify habitat suitability: maximum entropy (Maxent) and expert-based (Analytic Hierarchy Process). We used distance to wells, distance to water, NDVI, land cover, distance to roads, terrain shape and fence presence to parameterize the models. We then used the output of these models as cost surfaces to compare two common connectivity models, least-cost modeling (LCM) and circuit theory. Using pronghorn movement data from spring and fall migrations, we identified potential migration corridors by combining each habitat suitability model with each connectivity model. The best performing model combination was Maxent with LCM corridors across both seasons. Maxent out-performed expert-based habitat suitability models for both spring and fall migrations. However, expert-based corridors can perform relatively well and are a cost-effective alternative if species location data are unavailable. Corridors created using LCM out-performed circuit theory, as measured by the number of pronghorn GPS locations present within the corridors. We suggest the use of a tiered approach using different corridor widths for prioritizing conservation and mitigation actions, such as fence removal or conservation easements.
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    Lateralized activation of Cluster N in the brains of migratory songbirds.
    (Eur J Neurosci, 2007-02) Liedvogel, Miriam; Feenders, Gesa; Wada, Kazuhiro; Troje, Nikolaus F; Jarvis, Erich D; Mouritsen, Henrik
    Cluster N is a cluster of forebrain regions found in night-migratory songbirds that shows high activation of activity-dependent gene expression during night-time vision. We have suggested that Cluster N may function as a specialized night-vision area in night-migratory birds and that it may be involved in processing light-mediated magnetic compass information. Here, we investigated these ideas. We found a significant lateralized dominance of Cluster N activation in the right hemisphere of European robins (Erithacus rubecula). Activation predominantly originated from the contralateral (left) eye. Garden warblers (Sylvia borin) tested under different magnetic field conditions and under monochromatic red light did not show significant differences in Cluster N activation. In the fairly sedentary Sardinian warbler (Sylvia melanocephala), which belongs to the same phyolgenetic clade, Cluster N showed prominent activation levels, similar to that observed in garden warblers and European robins. Thus, it seems that Cluster N activation occurs at night in all species within predominantly migratory groups of birds, probably because such birds have the capability of switching between migratory and sedentary life styles. The activation studies suggest that although Cluster N is lateralized, as is the dependence on magnetic compass orientation, either Cluster N is not involved in magnetic processing or the magnetic modulations of the primary visual signal, forming the basis for the currently supported light-dependent magnetic compass mechanism, are relatively small such that activity-dependent gene expression changes are not sensitive enough to pick them up.
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    Natal emigration by both sexes in the La Pacifica population of mantled howlers: when do some stay?
    (Am J Primatol, 2008-02) Clarke, Margaret R; Glander, Kenneth E
    We have reported previously that all male and female mantled howlers emigrate from natal groups at Hacienda La Pacifica, Costa Rica. In the years since that report, a small number of juveniles have stayed in the natal group without experiencing a solitary phase. Here, we present a post hoc analysis on juvenile emigration in six groups of howlers under observation for varying amounts of time between 1972 and 2005. Our records revealed 139 juveniles for whom emigration status was certain, and 125 of these did emigrate. There was a significant association between presence of mother and emigration: juveniles without mothers were more likely to remain in their natal group (chi(1)(2) = 53.1, P<.0001). The mean age of emigration for all juveniles (n = 125) was 2.47 years (SD = 0.9, range = 1.5-6.5). There was no difference in age of emigration by adult male composition (one-male, multi-male, both), but juveniles of unknown sex emigrated younger than either known males or females (F(2,116) = 4.4, P<.02). For emigrating juveniles of known sex (n = 99), both males and females without mothers left at a later age than those with mothers (F(1,95) = 6.5, P<.02). Although philopatry or delayed emigration occurs in a few motherless animals, most males and females do emigrate from their natal groups at ages consistent with those reported for other species of howlers.
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    Night-time neuronal activation of Cluster N in a day- and night-migrating songbird.
    (Eur J Neurosci, 2010-08) Zapka, Manuela; Heyers, Dominik; Liedvogel, Miriam; Jarvis, Erich D; Mouritsen, Henrik
    Magnetic compass orientation in a night-migratory songbird requires that Cluster N, a cluster of forebrain regions, is functional. Cluster N, which receives input from the eyes via the thalamofugal pathway, shows high neuronal activity in night-migrants performing magnetic compass-guided behaviour at night, whereas no activation is observed during the day, and covering up the birds' eyes strongly reduces neuronal activation. These findings suggest that Cluster N processes light-dependent magnetic compass information in night-migrating songbirds. The aim of this study was to test if Cluster N is active during daytime migration. We used behavioural molecular mapping based on ZENK activation to investigate if Cluster N is active in the meadow pipit (Anthus pratensis), a day- and night-migratory species. We found that Cluster N of meadow pipits shows high neuronal activity under dim-light at night, but not under full room-light conditions during the day. These data suggest that, in day- and night-migratory meadow pipits, the light-dependent magnetic compass, which requires an active Cluster N, may only be used during night-time, whereas another magnetosensory mechanism and/or other reference system(s), like the sun or polarized light, may be used as primary orientation cues during the day.
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    Night-vision brain area in migratory songbirds.
    (Proc Natl Acad Sci U S A, 2005-06-07) Mouritsen, Henrik; Feenders, Gesa; Liedvogel, Miriam; Wada, Kazuhiro; Jarvis, Erich D
    Twice each year, millions of night-migratory songbirds migrate thousands of kilometers. To find their way, they must process and integrate spatiotemporal information from a variety of cues including the Earth's magnetic field and the night-time starry sky. By using sensory-driven gene expression, we discovered that night-migratory songbirds possess a tight cluster of brain regions highly active only during night vision. This cluster, here named "cluster N," is located at the dorsal surface of the brain and is adjacent to a known visual pathway. In contrast, neuronal activation of cluster N was not increased in nonmigratory birds during the night, and it disappeared in migrants when both eyes were covered. We suggest that in night-migratory songbirds cluster N is involved in enhanced night vision, and that it could be integrating vision-mediated magnetic and/or star compass information for night-time navigation. Our findings thus represent an anatomical and functional demonstration of a specific night-vision brain area.
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    Population genetic analyses reveal the African origin and strain variation of Cryptococcus neoformans var. grubii.
    (PLoS Pathog, 2012-02) Litvintseva, Anastasia P; Mitchell, Thomas G
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    Secondary transfer of adult mantled howlers (Alouatta palliata) on Hacienda La Pacifica, Costa Rica: 1975-2009.
    (Primates, 2010-07) Clarke, Margaret R; Glander, Kenneth E
    Natal emigration by male and female mantled howlers (Alouatta palliata), and subsequent immigration into breeding groups, is well documented for the free-ranging population on Hacienda La Pacifica, Costa Rica, but secondary transfer was considered rare (Glander in Int J Primatol 3:415-436, 1992). Population surveys in 1998 and 2006 caused us to question our assumptions and to re-evaluate our long-term data set from a post hoc perspective. We first identified all animals observed or captured as adults in more than one non-natal group anywhere in the population. We then systematically analyzed joining or leaving by adults in seven groups tracked for various times from 1975 to 2005 for patterns suggesting secondary transfer. Fourteen adults (nine females, five males) were found in two different non-natal groups as adults. In addition, one male and one female that became dominant and reproduced in their natal group later transferred to a second group, and one female was known to be a tertiary transfer. Data from the seven tracked social groups indicate that 35% of all the males and 29% of all the females were potential secondary transfers. In these groups, males leaving or joining was not associated with group size or absolute number of females. Females leaving or joining was not associated with group size or absolute number of males, but females left groups with more females and joined groups with fewer females. Both sexes left groups with unfavorable sex ratios for their sex and joined groups with sex ratios more favorable for their sex. Since a favorable sex ratio is associated with reproductive success in other howler populations, this suggests secondary transfer as a reproductive strategy. Other factors could also influence secondary transfer.