Natural Variation in Horn Size and Social Dominance and Their Importance to the Conservation of Black Rhinoceros

Article (PDF Available)inConservation Biology 12(3):708 - 711 · July 2008with383 Reads
DOI: 10.1111/j.1523-1739.1998.97207.x
Abstract
1 Program in Ecology, Evolution, and Conservation Biology, 1000 Valley Road, University of Nevada, Reno, NV 89512, U.S.A., email berger@unr.edu
    • "Because dehorning generates unnatural horn-size asymmetries that affect combat outcomes between males, dehorning may have had fitness consequences due to female assessment (perception) of male quality. Note that dehorning was discontinued as a conservation practice due to high neonate mortality; females use horns in neonate defense (Berger & Cunningham, 1998). "
    [Show abstract] [Hide abstract] ABSTRACT: In this chapter, I discuss case-studies that have used animal-cognition principles in conservation. I expand on four conceptual essays about the interface of behavior and conservation, which were previously published in The Conservation Behaviorist (TCB), a biannual periodical of the Animal Behavior Society’s Conservation Committee: Animal Cognition and Its Role in Conservation Behavior, Behavioral Unknowns: an Emerging Challenge for Conservation, Contribution of Animal Behavior Research to Conservation Biology, and Behavior and Conservation in the Galapagos. My specific goal here is to draw attention to the value of animal-cognition-based studies that relate to conservation —conducted mostly by conservation biologists needing to apply cognition principles in their work— remark on the cognitive concepts intrinsic to each case, and encourage discussion and research in the interface of animal cognition and conservation behavior.
    Full-text · Chapter · Jan 2014 · The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology
    • "The same authors reported that in 65% of 128 male : male Black Rhino interactions, males with larger horns dominated (after controlling for age, Berger & Cunningham 1998). However, Berger & Cunningham (1998) found that female Black Rhinos tended to dominate males, regardless of differences in horn sizes: suggesting that dehorning may have little impact in terms of undermining the ability of females to defend themselves and their calves against bulls. Trendler (2011) reported incidents of dehorned bulls being killed by horned cows and lesser bulls. "
    Full-text · Book · Jan 2011 · The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology
    • "Horn function in extant rhinoceros varies by species. For example, in black rhinoceros (Diceros bicornis), horn size is related to intrasexual dominance, and horns are directly used in male-male aggression (Berger and Cunningham, 1998), but similar variation in horn size has no effect on dominance or fight outcome in Indian rhinoceros (Rhinoceros unicornis; Dinerstein, 1991). Using extant rhinoceros horns as an analog for horns in Pachyrhinosaurus would thus not exclusively support either species recognition or sexual selection, but the possibility of tall horns as a visual display, coupled with sexual monomorphism, would favor species recognition as the driving factor in ceratopsian horn evolution (Padian et al., 2004). "
    [Show abstract] [Hide abstract] ABSTRACT: The horned dinosaur Pachyhinosaurus possesses rugose bony bosses across the skull roof in lieu of the projecting bony horn cores seen in most ceratopsians. This elaboration of typical ceratopsian ornaments provides an opportunity to test hypotheses of ceratopsian facial skin morphology and function. We analyze bone morphology and histology associated with several classes of skin features in extant amniotes using a classification tree analysis. We isolate key osteological and histological correlates for unpreserved skin structures, including both a pattern of pitting and resorption characteristic of muskox (Ovibos) frontal horn boss, and a pattern of metaplastic ossification characteristic of rhinoceros nasal horn boss. We also describe correlates for other skin features, such as epidermal scales and horn sheaths. Dermatocranial elements from centrosaurine ceratopsians are then examined for the same osteological and histological correlates. From this comparison we propose that the rugose bosses that replace horn cores in many centrosaurine dinosaurs, most notably Achelousaurus and Pachyrhinosaurus, were covered by a thick pad of cornified skin derived from the caudodorsal side of the primitive horn sheath comparable to the horny boss of extant muskoxen (Ovibos). We examine extant taxa with skin morphologies similar to Pachyrhinosaurus for consistent adaptive relationships between structure and behavior. We determine that high-energy headbutting is consistently associated with the acquisition of thick cornified pads, seen in muskoxen as well as helmeted hornbills [Buceros (=Rhinoplax) vigil] and African buffalo (Syncerus). The association of the bony ornaments of Pachyrhinosaurus with risky agonistic behaviors casts doubt on the role of species recognition as a primary selection pressure driving the diversity of all ceratopsian horns. We conclude that social selection (a broad form of intraspecific competition) is a more appropriate explanation for the diversity of centrosaurine ceratopsian ornaments in the Late Cretaceous.
    Full-text · Article · Sep 2009
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