A comparison of age estimation methods for the saiga antelope <i>Saiga tatarica</i>

Lundervold, M.; Langvatn, Rolf; Milner‐Gulland, E. J.

doi:10.2981/wlb.2003.054

Cited by 9 publications

(6 citation statements)

References 23 publications

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“…The only exceptions to this were calves in particularly dense areas of the aggregation for which litter size could not be unambiguously determined (2004, nZ16; 2005, nZ209); these were subsequently excluded from analyses involving litter size. Calves were aged using a combination of behavioural and physiological indicators designed and tested during past saiga fieldwork (Lundervold 2001;Lundervold et al 2003). Owing to the non-invasive sampling methods, employed because of the conservation status of the species, no data on individual adult females were obtained.…”

Section: Methodsmentioning

confidence: 99%

The ‘big spenders’ of the steppe: sex-specific maternal allocation and twinning in the saiga antelope

et al. 2007

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Reintroductions are important tools for the conservation of individual species, but recently more attention has been paid to the restoration of ecosystem function, and to the importance of carrying out a full risk assessment prior to any reintroduction programme. In much of the Highlands of Scotland, wolves (Canis lupus) were eradicated by 1769, but there are currently proposals for them to be reintroduced. Their main wild prey if reintroduced would be red deer (Cervus elaphus). Red deer are themselves a contentious component of the Scottish landscape. They support a trophy hunting industry but are thought to be close to carrying capacity, and are believed to have a considerable economic and ecological impact. High deer densities hamper attempts to reforest, reduce bird densities and compete with livestock for grazing. Here, we examine the probable consequences for the red deer population of reintroducing wolves into the Scottish Highlands using a structured Markov predator-prey model. Our simulations suggest that reintroducing wolves is likely to generate conservation benefits by lowering deer densities. It would also free deer estates from the financial burden of costly hind culls, which are required in order to achieve the Deer Commission for Scotland's target deer densities. However, a reintroduced wolf population would also carry costs, particularly through increased livestock mortality. We investigated perceptions of the costs and benefits of wolf reintroductions among rural and urban communities in Scotland and found that the public are generally positive to the idea. Farmers hold more negative attitudes, but far less negative than the organizations that represent them.

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Section: Methodsmentioning

confidence: 99%

The ‘big spenders’ of the steppe: sex-specific maternal allocation and twinning in the saiga antelope

et al. 2007

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“…Adult/juvenile status was determined by sight using head proportions and tooth eruption. This two-level age estimation in the field was shown to be accurate when compared with reliable age estimation using tooth eruption and wear (Lundervold, Langvatn & Milner-Gulland, 2003). On average 69.5 AE 5.5 (SE) females with known age and litter size were recorded from the spring cull per year and population for 42 years in total (except that 460 females were culled in the north-west Pre-Caspian in 1958).…”

Section: Saiga Embryo Datamentioning

confidence: 99%

“…In addition, data at the individual level were available from the Betpak-dala population (n =651 females; Fadeev & Sludskii, 1982;K¨uhl et al, 2007). For a subset, jaws were collected for detailed age estimation using tooth eruption and tooth wear analysis (n =651; Lundervold et al, 2003) and gutted body mass was measured using a hanging balance in Betpak-dala, Kazakhstan during 1966Kazakhstan during -1978.…”

Section: Saiga Embryo Datamentioning

confidence: 99%

Monitoring population productivity in the saiga antelope

Kühl

Mysterud

Grachev

et al. 2009

Animal Conservation

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Effective conservation requires a good understanding of factors causing variation in population growth rate. We here analyse the relationship between female age and fecundity in the saiga antelope Saiga tatarica tatarica, a critically endangered ungulate of the Eurasian steppes and semideserts, at both individual and population levels. Annual variation in age structure and twinning rates was investigated using long-term datasets, sampling a total of 3308 females in four populations over more than 40 years. Further, a new non-invasive method is presented, estimating twinning rates from both calves and placentas encountered during calving aggregation transects. At an individual level, the most parsimonious model for twinning rates included three age classes (1, 2 and Z3 years); however, the model with only two classes (1 and Z2 years) was competitive and particularly useful for monitoring because these two age classes can reliably be determined by direct observation in the field. Among yearlings, 77.4% were fecund and 11.7% twinned, whereas among older females 94.6% were fecund and 72.6% twinned. At a population level, annual variation in age structure (proportion Z2 years) correlated well with annual variation in twinning rate except in the north-west PreCaspian population. Our results suggest that the recent poaching-driven collapse in saiga numbers has potentially resulted in reductions in fecundity, which will have an impact on population growth rate. Our results highlight the potential for monitoring of twinning rate using non-invasive calving aggregation transects as a cost-effective additional tool to population counts for monitoring the status of this critically endangered species. These monitoring methods are also potentially transferable to other ungulate species.

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“…However, sport hunting can also play a role in driving species declines in some areas, as has been observed for elephants (Selier, Page, Vanak, & Slotow, 2014), leopards (Pitman, Swanepoel, Hunter, Slotow, & Balme, 2015) and lions (Bauer et al, 2015). An animal's age is a common metric used to guide the sustainable harvest and management of a number of species throughout the world (Berkeley, Hixon, Larson, & Love, 2004;Garel, Cugnasse, Hewison, & Maillard, 2006;Gipson, Ballard, Nowak, & Mech, 2000;Hiller, 2014;Lundervold & Langvatn, 2003). Simulation modelling studies recently identified the implementation of age restrictions on trophy harvests as a promising method for regulating sustainable sport hunting of large carnivores, including African lions (Creel et al, 2016;Packer et al, 2009;Whitman, Starfield, Quadling, & Packer, 2004).…”

Section: Introductionmentioning

confidence: 99%

Effective implementation of age restrictions increases selectivity of sport hunting of the African lion

Begg

Miller

Begg

2017

Journal of Applied Ecology

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Sport hunting of wildlife can play a role in conservation but can also drive population declines if not managed sustainably. Previous simulation modelling found that large felid species could theoretically be hunted sustainably by restricting harvests to older individuals that have likely reproduced. Several African countries currently use age‐based hunting for lions although the outcomes have yet to be evaluated in a wild population. Here we provide the first empirical evidence that a system of incentives sufficiently encouraged age‐based hunting and reduced offtake of a wild felid, thereby reducing the potential risk of unsustainable hunting on a threatened species. We examined long‐term hunting data and the lion population trend in Niassa National Reserve, Mozambique. To incentivise hunter compliance, a “points” system was developed, which rewards operators that harvest lions older than the 6‐year minimum trophy age recommended for sustainable hunting and penalises operators that hunt “underage” lions (<4 years). A key component of this system is the ecological application of key physical traits that predictably change with age in order to estimate (by hunters) and validate (by authorities) trophy individuals’ ages pre‐ and post‐mortem, respectively. Analysis of 138 lion hunts and 87 lion trophies from 2003 to 2015 revealed that after enforcement of age restrictions in 2006, hunters shifted harvests to suitably aged lions (>6 years), from 25% of offtakes in 2004 to 100% by 2014. Simultaneously, the number of lions and percentage of quota harvested decreased, resulting in lower lion offtakes. Following an initial decrease after enforcement of the ageing system, the percentage of hunts harvesting lions stabilised, demonstrating that hunters successfully located and aged older lions. Synthesis and applications. Evidence suggests that age restrictions combined with an incentive‐based points system regulated sport hunting and reduced pressure on the lion population. We attribute the successful implementation of this management system to: (1) committed, consistent enforcement by management authorities, (2) genuine involvement of all stakeholders from the start, (3) annual auditing by an independent third party, (4) the reliable, transparent, straightforward ageing process and (5) the simple, pragmatic points system for incentivising hunter compliance. Our study demonstrates that the use of age restrictions can increase the selectivity of sport hunting and lower trophy offtakes to reduce the possibility of unsustainable sport hunting negatively impacting species populations in the absence of reliable estimates of population size. It must be noted, however, that there was no measurable change in the lion numbers over the past decade that could be attributed to the implementation of this policy alone.

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A comparison of age estimation methods for the saiga antelope Saiga tatarica

Cited by 9 publications

References 23 publications

The ‘big spenders’ of the steppe: sex-specific maternal allocation and twinning in the saiga antelope

The ‘big spenders’ of the steppe: sex-specific maternal allocation and twinning in the saiga antelope

Monitoring population productivity in the saiga antelope

Effective implementation of age restrictions increases selectivity of sport hunting of the African lion

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