Spatially restricted occurrence and low abundance as key tools for conservation of critically endangered large antelope in West African savannah

The effective conservation of mammals on the brink of extinction requires an integrated socio-ecological approach, yet the updated ecological knowledge of species remains fundamental. This study brings spatiotemporal behaviour, population structure, age-specific survival rates, and population size estimate of the Western Derby eland (WDE) in the Niokolo Koba National Park (NKNP), Senegal, investigated during dry seasons 2017 and 2018. WDE was strongly localised in the core area of NKNP (< 5%), active throughout the day with the highest peak in the hottest daytime, with a mean group size 7.6 ± SE 8.9. The adult sex ratio was female-biased and showed low annual adult male survival rates. The population consisted of high proportion of juveniles, whilst adults did not exceed 40%. The estimated population density was 0.138 WDE/km2 (± 0.0102) and estimated size 195 WDE in NKNP (CI95 from 54 to 708 individuals). Findings highlighted that the WDE population has potential to expand in the NKNP, due to an underutilized capacity. The age-specific vital rates indicate adult males as the most vulnerable; suggesting either an increase in the large predators’ population, livestock encroachment pressure, and/or poaching. Findings imply that targeted monitoring with science-based interpretation may bring forward strong conservation solutions to the protected area management decision-makers.

National and subnational size estimation of female sex workers in Ghana 2020: Comparing 3-source capture-recapture with other approaches

Background Key Population size estimation (PSE) is instrumental for HIV/STI preventive, treatment and care services planning, implementation and delivery. The objective was to estimate the overall population of female sex workers (FSW) in all the 16 regions of Ghana using different PSE methods. Method Mapping of venues and complete enumeration of seaters was conducted at the formative stage prior to the bio-behavioral survey (BBS). Three PSE methods were used to derive the size estimates of FSW in the 16 regions. These include: Capture-recapture (CRC), service multiplier and three-source capture recapture (3SCRC) methods. The final choice of the estimation method used to estimate the roamer population was 3SCRC. This method was chosen because of its perfect record-linkage–hierarchic combination of three names that minimizes overmatching as well as the addition of an interaction term in the model which corrects for the dependencies in CRC. Results The total population size estimate of the female sex workers in the country obtained for roamers using capture re-capture was 41,746 (95% CI: 41,488–41,932). Using the service multiplier, the total population for both the roamers and seaters was 41,153 (95% CI: 37,242–45,984). The 3-source capture re-capture yielded 55,686 roamers FSW (95% CI: 47,686–63,686). The seater population was 4,363 FSW based on census/complete enumeration. The total population size estimate of FSW (seaters and roamers) in Ghana was 60,049 when 3SCRC and census were added. This represents about 0.76% of all estimated adult females aged 15-49yrs in Ghana. Conclusion We report population size estimates (PSE) for FSW in Ghana. These estimates are the results of 3SCRC. These findings provide a valid and reliable source of information that should be referenced by government officials and policymakers to plan, implement and provide HIV/STI preventive, treatment, and care services for FSW in Ghana.

Spatially restricted occurrence and low population abundance estimates as key tools for the conservation of the critically endangered large social antelope in West African savannah

The effective conservation of mammals on the brink of extinction requires an integrated socio-ecological approach, yet the updated ecological knowledge of species remains fundamental. This study brings spatiotemporal behaviour, population structure, age-specific survival rates, and population size estimate of the Western Derby eland (WDE) in the Niokolo Koba National Park (NKNP), Senegal, investigated during dry seasons 2017 and 2018. WDE was strongly localised in the core area of NKNP (< 5%), the most active during the hottest periods of the day, with a mean group size 7.6 ± SE 8.9. The adult sex ratio was female-biased and showed low annual adult male survival rates. The population consisted of high proportion of juveniles, whilst adults did not exceed 40%. The estimated population density was 0.138 WDE/km2 (± 0.0102) and estimated size 195 WDE in NKNP. Findings highlighted that the WDE population has potential to expand in the NKNP, due to an underutilized capacity. The age-specific vital rates indicate adult males as the most vulnerable; suggesting either an increase in the large predators’ population, livestock encroachment pressure, and/or poaching. Findings imply that targeted monitoring with science-based interpretation may bring forward strong conservation solutions to the protected area management decision-makers.

Assessing prey selection of snow leopard in Mt. Kangchenjunga, Nepal

In spring of 2012, we studied the feeding habits of snow leopard using a comprehensive approach that combines fecal genetic sampling, macro and microscopic analysis of snow leopard diets and direct observation of Naur and livestock in Kangchenjunga Conservation Area of east Nepal. Out of collected 88 putative snow leopard scat samples from 140 transects (290 km) in 27 (4*4 km2) sampling grid cells, 83% were confirmed to be from snow leopard. The genetic analysis accounted for 19 individual snow leopards (10 male and 9 female) with a mean population size estimate of 24 (95% CI: 19- 29), and an average density of 3.9 snow leopards/100 km2 within 609 km2. Total available prey biomass of Naur and Yak was estimated at 355,236 kg (505 kg yak/km2 and 78 kg Naur/km2). From the available prey biomass, we estimated snow leopards consumed 7% annually which was comprised of wild prey (49%), domestic livestock (45%), and 6% unidentified items. The estimated 47,736 kg Naur biomass gives a snow leopard-Naur ratio of 1: 59 on a weight basis. The proportion of young Naur was estimated at 17%, with an almost double predation rate at 28%. Predators such as common leopard and wolf share the same habitat and might compete with snow leopard for prey which will likely influence future predator-prey associations in KCA. Along with livestock insurance scheme improvement, there needs to be a focus on improved livestock guarding as well as engaging and educating local people to be citizen scientists on the importance of snow leopard conservation, involving them in long-term monitoring programs and promotion of ecotourism.

Assessing prey selection of snow leopard in Mt. Kangchenjunga, Nepal

In spring of 2012, we studied the feeding habits of snow leopard using a comprehensive approach that combines fecal genetic sampling, macro and microscopic analysis of snow leopard diets and direct observation of Naur and livestock in Kangchenjunga Conservation Area of east Nepal. Out of collected 88 putative snow leopard scat samples from 140 transects (290 km) in 27 (4*4 km2) sampling grid cells, 83% were confirmed to be from snow leopard. The genetic analysis accounted for 19 individual snow leopards (10 male and 9 female) with a mean population size estimate of 24 (95% CI: 19- 29), and an average density of 3.9 snow leopards/100 km2 within 609 km2. Total available prey biomass of Naur and Yak was estimated at 355,236 kg (505 kg yak/km2 and 78 kg Naur/km2). From the available prey biomass, we estimated snow leopards consumed 7% annually which was comprised of wild prey (49%), domestic livestock (45%), and 6% unidentified items. The estimated 47,736 kg Naur biomass gives a snow leopard-Naur ratio of 1: 59 on a weight basis. The proportion of young Naur was estimated at 17%, with an almost double predation rate at 28%. Predators such as common leopard and wolf share the same habitat and might compete with snow leopard for prey which will likely influence future predator-prey associations in KCA. Along with livestock insurance scheme improvement, there needs to be a focus on improved livestock guarding as well as engaging and educating local people to be citizen scientists on the importance of snow leopard conservation, involving them in long-term monitoring programs and promotion of ecotourism.

Breeding population increase and range expansion of the Great Crested Grebe Podiceps cristatus in southeastern Norway

The Great Crested Grebe Podiceps cristatus is listed as near-threatened on the Norwegian red list due to small population size, estimated in 2015 at 220–380 pairs. Population size is considered to be stable. Approximately one quarter of the population (50–100 pairs) is thought to occur in Oslo and Akershus, but this estimate is not based on detailed data, and the only previous systematic estimate was 90–100 pairs in 13 sites in 1982. In 2018, I conducted a comprehensive survey of all known and potential breeding sites to assess current population size in Oslo and Akershus. I recorded 233 pairs in 34 sites, suggesting a large increase in population size. To analyse the population increase in more detail, I collected all known records of Great Crested Grebes during the breeding season for the period 1995–2018. Analyses confirmed that there has been a strong increase, at a yearly rate of 4.2%. The increase was both due to increases in already established populations (69% of total increase), and establishment of new sites (31%). New sites were colonised in particular the last 10–15 years, and new sites were located gradually further away from the sites that were already used in 1982, indicating continuous range expansion. New sites were also located in smaller, less nutrient-rich lakes at higher elevations, perhaps indicating occupation of lower quality sites that could limit further population increase. Similar population increases have also occurred in other parts of the distribution range of Great Crested Grebes in Norway, and I present a new population size estimate for Norway at 531–634 pairs. Hence, the species no longer qualifies for red listing, and one may consider to downlist the species to least concern.

Population decline of the Eurasian Curlew in Akershus (southeastern Norway)

The Eurasian Curlew (Numenius arquata) is a species in decline, classified as near threatened (NT) worldwide, and vulnerable (VU) in Norway. In Akershus county, southeastern Norway, the population of breeding Eurasian Curlews was estimated at 50-60 pairs in 1982. No recent update exists of this population size estimate. In this study, we assessed the population size in 2017 in Akershus, and examined how the population size changed between 1971 and 2017 by using historical observation records of Eurasian Curlews. We estimated that there were 30 territories in Akershus in 2017 and found that the population declined by 47% since 1995 and 77% since 1971. In the period 1995-2017, the yearly rate of decline was 2.8%. We discuss possible reasons for the decline, such as intensive agricultural practices, high nest predation rates, and large-scale threats on the wintering grounds.

Robust Estimation of Recent Effective Population Size from Number of Independent Origins in Soft Sweeps

Estimating recent effective population size is of great importance in characterizing and predicting the evolution of natural populations. Methods based on nucleotide diversity may underestimate current day effective population sizes due to historical bottlenecks, whereas methods that reconstruct demographic history typically only detect long-term variations. However, soft selective sweeps, which leave a fingerprint of mutational history by recurrent mutations on independent haplotype backgrounds, holds promise of an estimate more representative of recent population history. Here, we present a simple and robust method of estimation based only on knowledge of the number of independent recurrent origins and the current frequency of the beneficial allele in a population sample, independent of the strength of selection and age of the mutation. Using a forward-time theoretical framework, we show the mean number of origins is a function of θ=2Nμ and current allele frequency, through a simple equation, and the distribution is approximately Poisson. This estimate is robust to whether mutants preexisted before selection arose and is equally accurate for diploid populations with incomplete dominance. For fast (e.g., seasonal) demographic changes compared with time scale for fixation of the mutant allele, and for moderate peak-to-trough ratios, we show our constant population size estimate can be used to bound the maximum and minimum population size. Applied to the Vgsc gene of Anopheles gambiae, we estimate an effective population size of roughly 6×107, and including seasonal demographic oscillations, a minimum effective population size >3×107, and a maximum <6×109, suggesting a mean ∼109.