Moschus Berezovskii Flerov, 1928)
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Use the following type of citation: North-western Journal of Zoology 2021: e211703 Paper Submitted to The North-Western Journal of Zoology 1 *Handling editor: Linas Balčiauskas 2 *Manuscript Domain: theriology 3 *Manuscript code: nwjz_21_TH_03 4 *Submission date: 04_02_2021 5 *Revised: 25_04_2021 6 *Accepted: 28_04_2021 7 *No. of words: 2513 8 9 Title of the paper: Age-related musk secretion and body weight in captive forest musk 10 deer (Moschus berezovskii Flerov, 1928) 11 Running head: Age-related musk secretion and weight Zoology 12 Authors (First LAST - without institution name!): Jing WANG, Robertof B. WELADJI, Xiuxiang MENG 13 Key Words (at least five keywords): Moschus berezovskii, musk secretion, senescence, body weight, 14 captive breeding. Journalpaper 15 No. of Tables: 1 16 No. of Figures: 3 accepted 17 No. of Files: 1 18 North-Western 19 Use the following type of citation: North-western Journal of Zoology 2021: e211703 nwjz-2 20 Age-related musk secretion and body weight in captive forest musk deer (Moschus 21 berezovskii Flerov, 1928) 22 Jing WANG1, Robert B. WELADJI2, Xiuxiang MENG1* 23 1. School of Environment and Natural Resources, Renmin University of China, Beijing 24 100872, China 25 2. Department of Biology, Concordia University, 7141 Sherbrooke Street West, Montreal, 26 Quebec, H4B 1R6, Canada 27 * Corresponding authors name and email address: Xiuxiang MENG, [email protected] 28 29 Abstract. Musk is a precious wildlife resource, secreted by adult male musk deer and having Zoology 30 role in rutting and reproduction. As predicted by senescenceof hypothesis, this sexual trait 31 should change wi. th age By investigating a captive forest musk deer (Moschus berezovskii 32 Flerov, 1928) population located in the western plateau of China from 2006 to 2018, we Journalpaper 33 assessed the relationship between animal age, body weight and musk secretion. Aging pattern 34 was found both in body weight and musk secretion. Body weight of males decreased from 10 35 years old, while musk secretion declinedaccepted from 4 years of age. The relationship between body 36 weight and musk secretion varied at different age classes. Musk secretion represented positive 37 correlation with bodyNorth-Western weight for individuals aged 1–4 years, while it was not obvious for 38 older males. Our results provide an understanding of endangered musk deer from the 39 perspective of age-related phenotypic and endocrine change, which can serve as a basis for 40 successful musk deer farming, sustainable musk production and improving ex situ 41 conservation. 42 43 Key words: Moschus berezovskii, musk secretion, senescence, body weight, captive breeding. 44 Use the following type of citation: North-western Journal of Zoology 2021: e211703 nwjz-3 45 Running title: age-related musk secretion and weight 46 47 Introduction 48 Senescence, a gradual decrease in fitness traits with advancing age (Ericsson et al. 2001, 49 Kroeger et al. 2018) commonly observed in mammals (Liu et al. 2012; Marangoni et al. 50 2016), is expressed by a progressive decline in reproduction value and performance or 51 survival rate while aging (Loison et al. 1999; Weladji et al., 2010). Senescence varies among 52 genders, species or populations and the underlying mechanism is controversial (Kirkwood & 53 Rose 1991; Bouwhuis et al. 2011). Age at onset of senescence in Norwegian female red deer 54 (Cervus elaphus Linnaeus, 1758) was after the age of 20 and 12 for males (Mysterud et al. Zoology 55 2001), which differ from fallow deer (Dama dama Linnaeus,of 1758), reaching senescence at 56 about 9 years old (McElligott et al. 2002). 57 Most senescence studies in animals have been tested from the perspective of survival and Journalpaper 58 reproduction traits. Other physiological or morphological traits, including body condition and 59 antler size of ungulates, that are also key factors of individual’s fitness and substantially affect 60 the survival and reproduction, have receivedaccepted little attention (Kroeger et al. 2018). Body mass 61 in reindeer (Rangifer tarandus Linnaeus, 1758), soay sheep (Ovis aries Linnaeus, 1758), red 62 deer and small bodyNorth-Western primates exhibit various patterns at senescence (Weladji et al. 2010; 63 Nussey et al. 2012; Mysterud et al. 2001; Hämäläinen et al. 2014), and the senescence in body 64 size which was the determinant of reproduction in females and competitive ability in males, 65 reflecting a fitness change and population dynamics (Bérubé et al. 1999). 66 Forest musk deer (Moschus berezovskii Flerov, 1929) is a small solitary forest ruminant. 67 Musk deer males possess a musk gland specialized for the musk production. It is situated 68 beneath the skin of the abdomen between reproductive organ and umbilicus (Wang & Harris 69 2015). Musk has been widely used in Asian traditional medicine as valuable medicinal Use the following type of citation: North-western Journal of Zoology 2021: e211703 nwjz-4 70 component and perfumery industry as fixative substances, and is even more expensive than 71 gold (Shrestha 1998, Yang et al. 2003). Musk has a strong musk odor owing to the muscone, 72 and it can be involved in chemical communication concerning maturity and reproduction 73 (Sokolov et al. 1986). Musk is secreted before rutting season, namely from May to July every 74 year and usually last for 3 to 7 days (Zhang 1983). During musk secretion, males musk deer 75 are less active and get easily excited, and they reduce and even stop feeding (Meng et al. 76 2006). Then, after almost two months’ maturity in the secretion pods, musk changes from 77 white paste without scent into significant scented red-brown substance. Associated with 78 males’ hormone change, the high energy-consumption secretion has been reported to be 79 affected by age, body condition, farming system, nutritional level and even feeding method Zoology 80 (Cheng et al. 2002, Guo et al. 2018), yet the senescence hypothesisof has not been tested using 81 those traits. In addition, the way age and other intrinsic factors specifically influence the musk 82 secretion has not been explored. Journalpaper 83 Here, we use a long-term individual-based data from a known-age male population of 84 captive forest musk deer located at western Sichuan plateau, China, to test the senescence 85 hypothesis on males’ musk secretion andaccepted body weight, and to assess the potential relationship 86 between musk secretion and body weight varies with age. Firstly, we assumed that body 87 weight and musk productionNorth-Western of musk deer decreased at a certain age due to senescence. 88 Individual performance typically peaks at the prime-age (Loison et al. 1999, Mysterud et al. 89 2005). We, therefore, expected that in prime-age body weight and musk production should be 90 higher than those in younger or older males. Secondly, we hypothesized for males that 91 capable of musk secretion, the body weight can be an indicator of health condition, and has 92 certain effects on the secretion. Being a secondary sexual trait, musk is costly to produce and 93 maintain, especially for the weak animals (Yang et al. 2003), suggesting that males with better 94 body condition should produce more musk. Hence, as body weight changes with age, patterns Use the following type of citation: North-western Journal of Zoology 2021: e211703 nwjz-5 95 of musk secretion may differ depending on the body weight at different age stage. Thus we 96 also hypothesized, that the relationship between body weight and male secretion will vary 97 with age classes. Our results can not only deepen the senescence understanding of ungulates, 98 also provide a basis of musk resources management. 99 100 Material and Methods 101 Study area 102 The data are from the Maerkang Musk Deer Breeding Center (MMDBC) in the western 103 plateau of Sichuan Province, China (31°53′N, 102°07′E), situated around 2600 m above the 104 sea level with an annual precipitation around 753 mm and with an average temperature of 8- Zoology 105 9°C, and characterized by dry winters and humid summers.of In the center, 1–3 males were kept 106 in a mud-grounded enclosure which consisted of a 10×10 m2 outdoor square and seven lined 107 brick cells, separated by iron-mesh fence, with 2 meters-high ceiling above the floor. All Journalpaper 108 animals were marked with ear tags once birth to realize individual identification with specific 109 age, and fed twice a day (around 5 minutes at dawn and dusk) by deer-keepers. The forage 110 was mostly fresh (in summer/spring) oraccepted dried leaves (in winter/fall) collected from the nearby 111 natural habitats of wild musk deer. 112 Data collection North-Western 113 Musk can be extracted from live males without harming their growth and following breeding, 114 which is conducted every year and sustainable (Shrestha 1998). In MMDBC, at the beginning 115 of October, male musk deer was physically restrained to be weighted. Meanwhile, a sterile 116 scoop with smooth edge and small groove at the end was gently inserted into musk pod, then 117 by rotating the scoop, the musk was extracted without hurts. For musk’s fully collection, the 118 pod was repeatedly pinched and pressed to make sure no substance left. Individual’s musk 119 was weighed in fresh once extracted outside, and the process was completed in 10 minutes by Use the following type of citation: North-western Journal of Zoology 2021: e211703 nwjz-6 120 the same experienced musk collector to minimize the musk loss and musk deer’s stress 121 response. In general, individual’s body weight and musk production of about 1259 122 ungonadectomized male forest musk deer was repeatedly measured in October, namely 2842 123 cases were recorded from 2006 to 2018.