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Burgess, Elizabeth A., Lanyon, Janet M.; Keeley, Tamara
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2012 |
Testosterone and tusks: maturation and seasonal reproductive patterns of live, free-ranging male dugongs (Dugong dugon) in a subtropical population.
Reproduction 143(5):683-697. 9 figures. DOI: 10.1530/REP-11-0434. May 1, 2012.
–ABSTRACT: Knowledge of male reproductive status and activity in free-ranging animals is vital to understanding reproductive patterns and population dynamics. Until now, almost all information regarding reproductive behavior of the dugong, a cryptic marine mammal, has relied on post-mortem examination. We examined the relationships between body length, tusk eruption (secondary sexual characteristic), seasonality, and group association on fecal testosterone metabolite concentrations in 322 free-ranging dugongs (159 males, 163 females) in subtropical Moreton Bay, Australia. Fecal testosterone concentrations demonstrated biologically meaningful differences in testicular activity between sexes and across reproductive/age classes, and were correlated with circulating concentrations in serum. Male dugongs have a pre-reproductive period that persists until a body length of 240 cm is achieved. Puberty apparently occurs between 240 and 260 cm body length when fecal testosterone levels increase fourfold (>500 ng/g) over juvenile levels, and is associated with tusk eruption. However, social maturity may be delayed until male dugongs are larger than 260 cm with well-developed tusks. In mature males, the lowest (<500 ng/g) fecal testosterone concentrations occur in the austral autumn months with maximal concentrations in September-October, coincident with the onset of a spring mating season. During spring, solitary mature males had fecal testosterone concentrations double those of mature males sampled within groups, potentially suggesting a mating strategy involving roving of reproductively active males. This study demonstrates that single-point physiological data from individuals across a population have value as indicators of reproductive processes. Our approach provides an efficacious non-lethal method for the census of reproductive status and seasonality in live male dugongs.
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Burgess, Elizabeth A.; Lanyon, Janet M.; Brown, Janine L.; Blyde, David; Keeley, Tamara
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2012 |
Diagnosing pregnancy in free-ranging dugongs using fecal progesterone metabolite concentrations and body morphometrics: a population application.
General and Comparative Endocrinology 177(1): 82-92. 2 tabs. 8 figs. DOI: 10.1016/j.ygcen.2012.02.008. May 15, 2012.
–ABSTRACT: Assessing reproductive status and monitoring reproductive rates is important in the effective management of vulnerable marine mammal species such as the dugong (Dugong dugon). Knowledge of the reproductive physiology of this species is limited, and determining reproductive parameters (e.g., sexual maturation, pregnancy, and reproductive senescence) has been restricted by a lack of non-lethal methods for assessing reproductive status in free-ranging individuals. The aim of this study was to develop a method to identify pregnant individuals in a wild dugong population. Using an enzyme immunoassay, we quantified concentrations of fecal progesterone metabolites (fP) in 322 dugongs, including confirmed pregnant females (n=10), presumed non-pregnant adult females (n=25), juvenile females (n=24), subadult females (n=41), adult females of unknown pregnancy state (n=63), and males of all sizes (n=159). External body morphometrics of each dugong were measured, and confirmation of pregnancy in adult female dugongs was determined by ultrasonography or observation of subsequent neonates. Concentrations of fP were different between sexes and reproductive size classes (P<0.001), and similar to 30-fold higher in confirmed pregnant dugongs (2017-7760ng/g) compared to presumed non-pregnant females (30-221ng/g), juvenile females (29-195ng/g), and males (24-261ng/g) (P<0.001). Body measures of maximum and anal girths, and teat length were all greater in confirmed pregnant females than presumed non-pregnant females (all P<0.05). We evaluated a Discriminant Function Analysis (DFA) to provide a model for predicting pregnant and non-pregnant dugongs. Cross-validated results showed that the DFA correctly classified 100% of pregnant and non-pregnant females using fP concentrations, body length, fineness ratio (an index of body shape), and teat length (a female reproductive trait). Using the DFA model, we classified the pregnancy status of all female dugongs and identified a total of 30 females as pregnant and 133 females as non-pregnant from the sampled population over the sample period. Pregnant dugongs in the Moreton Bay population are characterized by fecal progesterone metabolite concentrations>1000ng/g, body length>=260cm, maximum girth>=215cm, anal girth>=126cm, and teat length>=5cm long. In summary, analysis of fP concentrations in combination with body morphometrics may be used to diagnose pregnancy in free-ranging dugongs, and provides a new tool to monitor breeding rates of wild sirenian populations.
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Lanyon, Janet M.; Burgess, Elizabeth A.
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2014 |
Methods to examine reproductive biology in free-ranging, fully-marine mammals.
Reproductive Sciences in Animal Conservation (New York, Springer) 753: 241-274. DOI: 10.1007/978-1-4939-0820-2-11. June 26, 2014.
–ABSTRACT: Historical overexploitation of marine mammals, combined with present-day pressures, has resulted in severely depleted populations, with many species listed as threatened or endangered. Understanding breeding patterns of threatened marine mammals is crucial to assessing population viability, potential recovery and conservation actions. However, determining reproductive parameters of wild fully-marine mammals (cetaceans and sirenians) is challenging due to their wide distributions, high mobility, inaccessible habitats, cryptic lifestyles and in many cases, large body size and intractability. Consequently, reproductive biologists employ an innovative suite of methods to collect useful information from these species. This chapter reviews historic, recent and state-of-the-art methods to examine diverse aspects of reproduction in fully-aquatic mammals.
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Merson, Samuel D.; Ouwerkerk, Diane; Gulino, Lisa-Maree; Klieve, Athol V.; Bonde, Robert K.; Burgess, Elizabeth A.; Lanyon, Janet M.
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2014 |
Variation in the hindgut microbial communities of the Florida manatee, Trichechus manatus latirostris over winter in Crystal River, Florida.
FEMS Microbiology Ecology 87(3): 601-615. 5 tabs. 5 figs. DOI: 10.1111/1574-6941.12248. Mar. 2014.
–ABSTRACT: The Florida manatee, Trichechus manatus latirostris, is a hindgut-fermenting herbivore. In winter, manatees migrate to warm water overwintering sites where they undergo dietary shifts and may suffer from cold-induced stress. Given these seasonally induced changes in diet, the present study aimed to examine variation in the hindgut bacterial communities of wild manatees overwintering at Crystal River, west Florida. Faeces were sampled from 36 manatees of known sex and body size in early winter when manatees were newly arrived and then in mid-winter and late winter when diet had probably changed and environmental stress may have increased. Concentrations of faecal cortisol metabolite, an indicator of a stress response, were measured by enzyme immunoassay. Using 454-pyrosequencing, 2027 bacterial operational taxonomic units were identified in manatee faeces following amplicon pyrosequencing of the 16S rRNA gene V3/V4 region. Classified sequences were assigned to eight previously described bacterial phyla; only 0.36% of sequences could not be classified to phylum level. Five core phyla were identified in all samples. The majority (96.8%) of sequences were classified as Firmicutes (77.3 ± 11.1% of total sequences) or Bacteroidetes (19.5 ± 10.6%). Alpha-diversity measures trended towards higher diversity of hindgut microbiota in manatees in mid-winter compared to early and late winter. Beta-diversity measures, analysed through PERMANOVA, also indicated significant differences in bacterial communities based on the season.
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Lanyon, Janet M.; Athousis, Chrissa; Sneath, Helen L.; Burgess, Elizabeth A.
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2021 |
Body scarring as an indicator of social function of dugong (Dugong dugon) tusks.
Mar. Mamm. Sci. 37(3): 962-981. https://doi.org/10.1111/mms.12788 July 7, 2021 (publ. online Feb. 26, 2021).
–ABSTRACT: The fully aquatic lifestyle of dugongs means that direct observation of social tusk use is not usually possible. This study used body scarring as an indicator of tusk function by males. Tusk rake scars on 298 live wild dugongs, of both sexes and all sizes, were categorized and counted in over 1,000 photographs, and examined in relation to maturity and reproductive activity over seasons. All dugongs had tusk scars, but adults were the main recipients. Sexually active adults acquired the greatest number of fresh tusk wounds during the mating season. Subadults received fresh rakes at similar numbers year?round. Adult males had more scars on the mid and posterior dorsum, indicating that males direct combative force to these regions of the male body when competing for females. Adult females had heaviest scarring and more tusk puncture wounds on the anterior?mid dorsum and head, suggesting that male dugongs use tusks in sexual coercion. Heavy scarring sustained by solitary calves compared to dependent ones, suggests that mothers afford some protection. Body scarring caused by tusks may serve as an indicator of reproductive contribution of the recipients, providing that successful males are involved in more reproductive competitions, and successful females in more mating events.
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Smoll, Laetitia I, Keeley,Tamara , Burgess, Elizabeth A. Lanyon, Janet M.
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2024 |
Measuring steroid hormone levels in the skin of free-ranging dugongs: A less invasive way to determine reproductive status.
Marine Mammal Science https://doi.org/10.1111/mms.13206. Nov. 22, 2024.
–ABSTRACT: Monitoring hormone concentrations in marine mammals provides valuable information regarding reproductive status and health. Skin is potentially useful for measuring hormone levels and can often be collected without capture. We investigated whether progesterone, testosterone, and cortisol could be measured in skin from dugongs using enzyme immunoassays. Hormones were measured in dorsal skin scrapings from free-ranging dugongs, including known pregnant females, nonpregnant adult females, reproductively active males, and reproductively inactive males, each identified using fecal progesterone or testosterone concentrations. Progesterone could be detected reliably in skin, with significantly higher mean progesterone concentrations (118.2 ? 6.6 ngg-1) in pregnant females than all other groups (60.8 ? 4.2 ngg-1). Male dugongs had higher skin testosterone concentrations than females, although testosterone levels were not detectable in some samples and could not discriminate reproductively active from inactive males. Cortisol was detectable in 8 of 40 skin samples only. Although refinement of this method is required for improved hormone recovery and additional validation is warranted, our findings demonstrate proof of concept for the use of epidermal skin samples to measure steroid hormones in dugongs and offer a method of diagnosing pregnancy in dugongs without the need for capture.
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Bibliography and Index of the Sirenia and Desmostylia 