Forest elephant (<i>Loxodonta africana cyclotis</i>) stature in the Réserve de Faune du Petit Loango, Gabon

Morgan, Bethan J.; Lee, Phyllis C.

doi:10.1017/s0952836902003291

Cited by 24 publications

(31 citation statements)

References 22 publications

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“…Noninvasive photogrammetric methods are commonly used to investigate body length of marine mammals (Perryman and Lynn, 1993;Perryman and Westlake, 1998) but have rarely been applied to terrestrial mammals (elephants (Loxodonta spp. ): (Lee and Moss, 1995;Morgan and Lee, 2003;Shrader et al, 2006), baboons (Papio spp. ): (Kitchen et al, 2003), and estimates of sexual swellings in chimpanzees (Pan troglodytes) (Domb and Pagel, 2001;Emery and Whitten, 2003;Deschner et al, 2004).…”

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confidence: 99%

Using photogrammetry and color scoring to assess sexual dimorphism in wild western gorillas (Gorilla gorilla)

Breuer

Robbins

Boesch

2007

American J Phys Anthropol

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Investigating sexual dimorphism is important for our understanding of its influence on reproductive strategies including male-male competition, mate choice, and sexual conflict. Measuring physical traits in wild animals can be logistically challenging and disruptive for the animals. Therefore body size and ornament variation in wild primates have rarely been quantified. Gorillas are amongst the most sexually dimorphic and dichromatic primates. Adult males (silverbacks) possess a prominent sagittal crest, a pad of fibrous and fatty tissue on top of the head, have red crest coloration, their saddle appears silver, and they possess a silverline along their stomach. Here we measure levels of sexual dimorphism and within-male variation of body length, head size, and sexual dichromatism in a population of wild western gorillas using photogrammetry. Digital photogrammetry is a useful and precise method to measure sexual dimorphism in physical traits yielding sexual dimorphism indices (ISD), similar to those derived from traditional measurements of skeletal remains. Silverbacks were on an average 1.23 times longer in body length than adult females. Sexual dimorphism of head size was highest in measures of crest size (max ISD: 60.4) compared with measures of facial height (max ISD: 24.7). The most sexually dimorphic head size measures also showed the highest within-sex variation. We found no clear sex differences in crest coloration but there was large sexual dichromatism with high within-male variation in saddle coloration and silverline size. Further studies should examine if these sexually dimorphic traits are honest signals of competitive ability and confer an advantage in reproductive success.

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confidence: 99%

Using photogrammetry and color scoring to assess sexual dimorphism in wild western gorillas (Gorilla gorilla)

Breuer

Robbins

Boesch

2007

American J Phys Anthropol

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“…Despite similarities in growth schedules between populations, researchers using the predictive equation from the Amboseli data should be cautious when applying it to forest elephants L. cyclotis who have markedly different morphologies, and presumably, growth rates. Morgan & Lee (2003) suggest a 35-40% height difference between forest and savanna elephants. The difference between maximum bolus diameters of the two populations, however, is only 11% (18 cm in Amboseli savanna elephants and 16 cm in Petit Loango forest elephants) and the difference between minimum diameters is 15% (4.75 cm in Amboseli and 4 cm in Petit Loango) (Morgan & Lee, 2003).…”

Section: Discussionmentioning

confidence: 96%

“…Morgan & Lee (2003) suggest a 35-40% height difference between forest and savanna elephants. The difference between maximum bolus diameters of the two populations, however, is only 11% (18 cm in Amboseli savanna elephants and 16 cm in Petit Loango forest elephants) and the difference between minimum diameters is 15% (4.75 cm in Amboseli and 4 cm in Petit Loango) (Morgan & Lee, 2003). More data on bolus size are required from forest areas to assess the extent to which populations vary in bolus size.…”

Section: Discussionmentioning

confidence: 96%

“…Several methods have been used to estimate age to describe population age structure and dynamics accurately. *All correspondence to: S. Alberts E-mail: alberts@duke.edu Elephant age has been estimated using measurements of shoulder height (Hanks, 1972;Sukumar, Joshi & Krishnamurthy, 1988;Lindeque & Jaarsveld, 1993;Lee & Moss, 1995), back length (Croze, 1972), molar tooth wear and progression (Laws, 1966;Jachmann, 1988;Lindeque, 1991), hind footprint length (Western, Moss & Georgiadis, 1983;Lindeque & Jaarsveld, 1993;Lee & Moss, 1995) and dung bolus circumference or diameter (Jachmann & Bell, 1984;Reilly, 2002;Morgan & Lee, 2003). Each of these techniques has drawbacks.…”

Section: Introductionmentioning

confidence: 99%

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Measures of dung bolus size for known‐age African elephants (Loxodonta africana): implications for age estimation

et al. 2005

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The availability of a population of mostly known-age African elephants Loxodonta africana from Amboseli National Park, Kenya, provided a unique opportunity to assess the use of dung bolus diameter for estimating age. A predictive equation for estimating dung bolus diameters from elephants of known age was derived and was found to follow the typical growth pattern exhibited by changes in shoulder height and foot length. The relationship between measurements of dung bolus and age was particularly strong when growth rates were high (age 0-25 years). The dung bolus growth curve from Amboseli elephants was similar to that derived from another wild population of African elephants, suggesting that dung bolus diameter can be used to assess age structure in areas where it is impossible to construct independent prediction curves of age and dung bolus.

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“…Numerous factors could influence body size differences among different populations of a species [3]. The most recognized examples may be found in fisheries biology because overfishing can change population structures, shorten the life span of individuals, and impose selective pressure on life history traits, among other effects [4].…”

Section: Introductionmentioning

confidence: 99%

Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan

Hsu

Soong

2017

PLoS ONE

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Numerous environmental factors can influence body size. Comparing populations in different ecological contexts is one potential approach to elucidating the most critical of such factors. In the current study, we found that the body size of the land hermit crab Coenobita rugosus was significantly larger on Dongsha Island in the South China Sea than on other eco-islands around Southern Taiwan. We hypothesized that this could be due to differences in (1) shell resources, (2) parasite impact, (3) competition, (4) predation, and (5) food. We found no supporting evidence for the first three hypotheses; the shells used by the hermit crabs on Dongsha were in poorer condition than were those used elsewhere, extremely few individuals in the region had ectoparasites, and the density of hermit crabs varied considerably among localities within each island. However, significantly higher percentages of C. rugosus reached age 3 years on Dongsha than at Siziwan bay in Taiwan. Two growth rate indices inferred from size structures suggested faster growth on Dongsha than at Siziwan. The condition index (i.e., the body mass/shield length ratio of C. rugosus) was also greater on Dongsha than at Siziwan. Therefore, Dongsha hermit crabs seem to have superior diet and growth performance. Seagrass debris accumulation at the shore of Dongsha was considerable, whereas none was observed at Siziwan or on the other islands, where dicot leaves were the dominant food item for the vegetarian hermit crabs. We then experimentally evaluated the possible role of seagrass as food for C. rugosus. The crabs on Dongsha preferred seagrass to dicot leaves, and their growth increment was faster when they fed on seagrass than when they fed on dicot leaves; no such differences were found in the Siziwan hermit crabs. The aforementioned results are compatible with the food hypothesis explaining the size differences among the islands. The predator hypothesis could explain the greater life span but not the other findings. Populations of C. rugosus on islands with seagrass debris piles probably contribute more to the gene pool of the species because higher proportions of these populations could achieve high fecundity. The fate of these terrestrial hermit crabs may rely on the health of underwater seagrass ecosystems that are under threat from global change.

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Forest elephant (Loxodonta africana cyclotis) stature in the Réserve de Faune du Petit Loango, Gabon

Cited by 24 publications

References 22 publications

Using photogrammetry and color scoring to assess sexual dimorphism in wild western gorillas (Gorilla gorilla)

Using photogrammetry and color scoring to assess sexual dimorphism in wild western gorillas (Gorilla gorilla)

Measures of dung bolus size for known‐age African elephants (Loxodonta africana): implications for age estimation

Mechanisms causing size differences of the land hermit crab Coenobita rugosus among eco-islands in Southern Taiwan

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