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Worldwide savanna monkey (Chlorocebus spp.) body measures

Citation

Schmitt, Christopher A. et al. (2021), Worldwide savanna monkey (Chlorocebus spp.) body measures, Dryad, Dataset, https://doi.org/10.5061/dryad.vt4b8gtss

Abstract

Objectives: Direct comparative work in morphology and growth on widely dispersed wild primate taxa is rarely accomplished, yet critical to understanding ecogeographic variation, plastic local varia- tion in response to human impacts, and variation in patterns of growth and sexual dimorphism. We investigated population variation in morphology and growth in response to geographic variables (i.e., latitude, altitude), climatic variables (i.e., temperature and rainfall), and human impacts in the vervet monkey (Chlorocebus spp.).

Methods: We trapped over 1,600 wild vervets from across Sub-Saharan Africa and the Caribbean, and compared measurements of body mass, body length, and relative thigh, leg, and foot length in four well-represented geographic samples: Ethiopia, Kenya, South Africa, and St. Kitts & Nevis.

Results: We found significant variation in body mass and length consistent with Bergmann’s Rule in adult females, and in adult males when excluding the St. Kitts & Nevis population, which was more sexually dimorphic. Contrary to Rensch’s Rule, although the South African population had the largest average body size, it was the least dimorphic. There was significant, although very small, variation in all limb segments in support for Allen’s Rule. Females in high human impact areas were heavier than those with moderate exposures, while those in low human impact areas were lighter; human impacts had no effect on males.

Conclusions: Vervet monkeys appear to have adapted to local climate as predicted by Bergmann’s and, less consistently, Allen’s Rule, while also responding in predicted ways to human impacts. To better understand deviations from predicted patterns will require further comparative work in vervets.

Methods

The data derive from field collections made over many years using a common protocol: Ethiopia in 1973, Kenya in 1978-79; South Africa in 2002–2008, and several African countries and the Caribbean in 2009– 2011 in collaboration with the International Vervet Research Consortium (Jasinska et al., 2013). The International Vervet Research Consortium is a multidisciplinary research group that has, in addition to morphological variation, studied variation in patterns of growth and development (Schmitt et al., 2018), genetic/genomic (Jasinska, et al., 2013; Schmitt et al., 2018; Svardal et al., 2017; Turner et al. 2016a; Warren et al. 2015) and transcriptomic (Jasinska et al., 2017) variation, SIV immune response (Ma et al., 2013, 2014; Svardal et al., 2017), hor- monal variation (Fourie et al., 2015), C4 isotopes variation in hair (Loudon et al., 2014), gut parasite and disease variation (Gaetano et al., 2014; Senghore et al., 2016), genital morphology and appearance (Cramer et al., 2013; Rodriguez et al., 2015a,b), and other biological parameters within the genus Chlorocebus.

Vervet monkeys were trapped at locations across sub-Saharan Africa, including South Africa, Botswana, Zambia, Ethiopia, The Gambia, Ghana, and on the Caribbean islands of St. Kitts and Nevis (Figure 1). Trapping in Africa employed individual drop traps as described by Brett, Turner, Jolly, & Cauble (1982) and Grobler and Turner (2010), while trapping in St. Kitts and Nevis was done by local trappers using large group traps (Jasinska et al., 2013). Animals were anesthetized while in the trap and then removed to a processing area. Sex was determined by visual and manual inspection, while age classes were assigned from dental eruption sequences and based on previous observations (Table 2). All animals were weighed with either an electronic or hanging scale, and measured with a tape measure and sliding calipers. Parameters and protocols describing all measurements are available through the Bones and Behavior Working Group (2015; http://www.bonesandbehavior. org/). All animals were released to their social group after sampling and recovery from anesthesia. Observations during trapping allowed us to confirm the animals’ social group and local population affiliation.

For the present study, we chose metrics representative of skeletal size (body length, thigh length, leg length, and foot length) and body mass from a total of 1,613 vervets in four geographically and genomi- cally distinct populations: Ch. aethiops in Ethiopia, Ch. p. hilgerti in Kenya, Ch. p. pygerythrus in South Africa, and Ch. sabaeus on the Carib- bean islands of St. Kitts and Nevis (Table 3). The Caribbean populations are known to be descended from West African Ch. sabaeus brought to the Caribbean several hundred years ago (Warren et al., 2015). Of the whole sample, 288 females and 460 males were dentally immature. Sexual maturity is typically not reached in vervets until near the time of canine tooth eruption, here denoting the beginning of dental age 6 (Cramer et al., 2013; Rodriguez et al., 2015a); although somatic and skeletal growth often continues beyond the emergence of the third molar, which is here denoted as adult (Bolter & Zihlman, 2003). As is common, dental age and skeletal age are presumed to be similarly cor- related across the genus, meaning that comparable dental age implies comparable skeletal developmental age across populations (Seselj, 2013).

All measurements were developed by CJJ and TRT and other measurers (CAS and JDC) were trained directly by TRT. During training, repeated measures of the same individual were conducted in tandem with TRT until concordance was reached.

The location of each trapping site is reported in decimal degrees (Table 1), and for most sites measured using hand-held GPS units. For those trapping sites lacking GPS readings, a general latitude and longi- tude for the trapping area (e.g., game reserve, town) was used. Human impact at each trapping location was assessed according to conditions during the time of trapping using a previously published index devel- oped by Pampush (2010) to study variation in vervet body size, and subsequently used by Loudon et al. (2014) and Fourie et al. (2015) (Table 1). This index includes presence/absence measures of reliable access to (1) agricultural land, (2) human food, (3) rubbish or garbage dumps, and (4) whether animals are regularly provisioned, as well as a three-level scale of human activity within the presumed home range of the group (low, moderate, or high). In the index, point values are assigned to each value, with the lowest tier of human impact each receiving a 1, scaling up by 1 for each level. Added together, these val- ues comprise a human impact group ranging from low (lowest score in each category; index 5 5), to moderate (index 5 6–8), to high (index- 5 9–11). These measures take into account only the ecological impact of humans, and do not address local ecological variables (such as native plant productivity) that might also influence body size and growth. As a proxy for these measures, we collected several climatic variables for trapping sites from the WorldClim 2 database, which has a spatial reso- lution of about 1 km2 (Fick & Hijmans, 2017). Climatic variables consid- ered for inclusion in our models were (1) annual mean temperature (in degrees Celsius), (2) temperature seasonality (measured as the standard deviation of annual mean temperature multiplied by 100), (3) the mini- mum temperature of the coldest month (in degrees Celsius), (4) the mean temperature of the coldest quarter of the year, (5) annual precipi- tation (in mm), and (6) precipitation seasonality (measured as thecoefficient of variation of monthly precipitation). Climate data were accessed via the R package raster v. 2.6-7 (Hijmans & van Etten, 2012), and assigned to trapping sites based on latitude and longitude.

Usage Notes

Along with the ReadMe file (in Excel format), which describes all variables in the dataset, there is also an html file with R code used for analyses in the publication which will be uploaded to accompany the dataset.

Funding

National Science Foundation, Award: BCS 0938969

National Science Foundation, Award: BNS 770-3322

National Science Foundation, Award: SOC 74-24166

National Institutes of Health, Award: R01RR0163009

National Institutes of Health, Award: R01OD010980

NSF, Award: BN770‐3322

NSF, Award: SOC 74‐24166

NSF, Award: BCS 0938969

Fulbright Foundation in Greece

National Center for Research Resources, Award: R01OD010980/OD/NIH

National Center for Research Resources, Award: R01RR016300/RR/NCRR