Wet season range fidelity in a tropical migratory ungulate

Abstract

Summary1. In migratory populations, the degree of fidelity and dispersal among seasonal ranges is an important population process with consequences for demography, management, sensitivity to habitat change and adaptation to local environmental conditions. 2. Characterizing patterns of range fidelity in ungulates, however, has remained challenging because of the difficulties of following large numbers of marked individuals across multiple migratory cycles and of identifying the appropriate scale of analysis. 3. We examined fidelity to wet season (i.e. breeding) ranges in a recently declining population of wildebeest Connochaetes taurinus Burchell in northern Tanzania across 3 years. We used computer-assisted photographic identification and capture-recapture to characterize return patterns to three wet season ranges that were ecologically discrete and topographically isolated from one another. 4. Among 2557 uniquely identified adult wildebeest, we observed 150 recaptures across consecutive wet seasons. Between the two migratory subpopulations, the probability of remaining faithful to wet season areas ranged between 0AE82 and 1AE00. Animals from a non-migratory segment of the population (near Lake Manyara National Park) were rarely observed in other wet season ranges, despite proximity to one of the migratory pathways. 5. We found no effect of sex on an individuals' probability of switching wet season ranges. However, the breeding status of females in year i had a strong influence on patterns of range selection in year i + 1, with surviving breeders over three times as likely to switch ranges as non-breeders. 6. Social-group associations between pairs of recaptured animals were random with respect to an individual's wet season range during the previous or forthcoming wet seasons, suggesting that an individual's herd identity during the dry season does not predict wet season range selection. 7. Examining fidelity and dispersal in terrestrial migrations improves our understanding of the constraints that migrants experience when they face rapid habitat changes or fluctuations in environmental conditions.

Computer-Assisted Photo Identification Outperforms Visible Implant Elastomers in an Endangered Salamander, Eurycea tonkawae

“…Given the low initial error rates observed with Wild-ID, we did not test other software platforms nor attempt to further optimize the Wild-ID scoring algorithm. Photo ID applications aimed at species with more challenging natural marking patterns [20] or species with evolving marks [19] may require either optimization of the Wild-ID scoring algorithm [13] or modeling of the error process. Indeed, new methods are already being developed to accommodate photoID errors in capture-recapture modeling [30] including errors involving evolving natural marks [16].…”

“…1.0.1 [13]; http://www.dartmouth.edu/~envs/faculty/bolger.html). To date, Wild-ID has been used to accurately identify wildebeest ( Connochaetes taurinus [20]) and giraffe ( Giraffa camelopardis [13]). This software uses the SIFT (Scale Invariant Feature Transform) algorithm to characterize variable patterns within photographs and compare all combinations of photographs in a database [21].…”

Benefits of migration in a partially-migratory tropical ungulate

“…[13,15-17,20,21,23]) but it has only recently been described in a few tropical ungulates (African buffalo Syncerus caffer [19]; wildebeest [47]). Our findings constitute the first description to our knowledge of a partial migration pattern in an impala population.…”

“…[18]) or to a wet season range in a tropical ungulate (e.g. [47]) is considered to provide benefits related to familiarity with the location of resources, predators or conspecifics [53]. The impalas that we monitored had all been introduced at the same release site located in the south range (Figure 1) which therefore may be more familiar than the north range and may provide some predator-avoidance benefits.…”

A multi-method approach to delineate and validate migratory corridors

“…The approximate boundaries of the TE are Lake Natron to the north, Simanjiro plains to the southeast, and Irangi Hills to the southwest, with the Rift Valley 110 escarpment forming the western boundary (Lamprey 1964;Morrison and Bolger 2012). Rain occurs almost exclusively from November-May.…”