Globally, the grey-headed albatross Thalassarche chrysostoma is listed as Endangered due to decreasing populations at its major breeding colonies. We analysed the population trend at Marion Island using annual counts of incubating pairs and fledglings from 1984 to 2021 and three methods: TRends and Indices for Monitoring data (TRIM), a generalized additive model and a state-space model. In contrast to rapid decreases at most other colonies, all three methods indicated a local population increase at an average annual rate of 1.3%. The latter two models indicated a decreasing trend from 1997 to 2002, presumably related to mortality on longlines set for Patagonian toothfish Dissostichus eleginoides around the island, which peaked from 1996 to 1998. Grey-headed albatrosses exhibit greater variation in annual counts than other seabird species at Marion Island, possibly linked to interannual variation in breeding success because they are biennial breeders. However, breeding success alone was not significant in any of the models, presumably because it cannot capture the complexities of both population processes and environmental variation. Although all three models predicted the overall trends well, integrated population models, which can account for demographic processes, might be more appropriate to model long-term population trends.

Hong Kong is one of the busiest metropolises, and the Eurasian otter Lutra lutra is one of its most threatened species. We collected published data for 1890–2020 to document changes in local otter abundance and distribution over time. The 108 records revealed new distribution data and showed that decline began as early as the 1930s. The local Eurasian otter is strongly associated with coastal and alluvial wetlands, and its last refugium, the Yuen Long floodplain draining the Mai Po Inner Deep Bay Ramsar Site, has always been a critical habitat. Our analysis suggests that hunting is unlikely to be a major cause of the otter's decline. Rather, dependence on lowland wetlands makes it particularly susceptible to habitat loss caused by increasing urbanization. Auxiliary infrastructures and water pollution have also exacerbated wetland degradation to the detriment of otters and their prey. There is a need for greater cooperation amongst government agencies and landowners to guarantee otter survival: priority steps include the establishment of additional and interconnected wetland reserves, better stakeholder engagement and enforcement efficiency to tackle entrenched pollution problems, and flood prevention schemes that preserve or restore functional riverine ecosystems within critical otter habitats. The current otter distribution range has been earmarked for development in a government-led mega urbanization plan; the plight of the local Eurasian otter needs to be widely publicized to garner stakeholders' support and galvanize immediate conservation actions across society.

Population size and geographical range are the key quantitative criteria used by the IUCN to assess the conservation status of a species. However, such information is often incomplete and inconsistent, even for seemingly abundant species. To assess the population and conservation status of Indian primates, we conducted a systematic review of recent research using the searching, appraisal, synthesis and analysis (SALSA) approach. We reviewed a total of 41 studies on Indian primates conducted during the last 2 decades (2000–2021) for information on various parameters that influence their conservation. We found that 20 out of a total of 26 primate species were evaluated for their population status, and the majority of these studies (71%) showed an overall declining population trend. Remarkably, all but one of the studies conducted exclusively within protected areas revealed declining population trends, whereas trends were more variable for primate populations in non-protected areas. Our data indicate that only 27% (n = 7) of Indian primate species have been surveyed or re-surveyed to assess their population status within the last 5 years. Although threats vary in time and space from species to species, 78% of the studies recorded natural system modifications including habitat loss and fragmentation among the main threats to the survival of Indian primates. Most studies on the population status of Indian primates have either been spatially limited or used outdated methods. We recommend that future studies adopt robust techniques to estimate populations and work across larger geographical scales to develop effective management strategies for the conservation of primates in India.

The Tarim red deer Cervus hanglu has been recently recognized as a separate deer species with populations in China, Central Asia and Kashmir. These populations are few, isolated and at risk of extinction. The documented range of the Kashmir population of the hangul, now recognized as Cervus hanglu hanglu, is restricted to c. 808 km2 and comprises < 200 individuals, confined mainly to the 141 km2 Dachigam National Park. A few relict herds inhabit the surrounding landscape. Here we analyse the results of almost 20 years of population monitoring (January 2001–March 2020). We found that this population is unable to increase despite full protection within Dachigam National Park. We performed a population viability analysis using both deterministic and stochastic simulations and found that further population decrease is likely. We recommend the use of improved monitoring methods to investigate the population dynamics of the hangul and the implementation of measures to reduce the risk of extinction faced by this small population. Science-based conservation policies, including ex situ conservation and reintroduction programmes, will be required to increase the hangul population size and range.

There is ever-greater need for information about changing marine biodiversity, but such information is sparse at large spatial or temporal scales. Records about distributions of species collected by volunteers can fill gaps in knowledge that cannot yet be addressed by more structured sampling. Bayesian occupancy models show great promise for estimating trends in occurrence of species through time. This study uses the Sparta occupancy model with records from the Seasearch programme from coastal waters of Britain and Ireland during the period 2000–2020, focussing on three species of Crustacea (Cancer pagurus, Homarus gammarus and Palinurus elephas). Populations of P. elephas crashed in the 1970s, but now appear to be re-establishing in south-west England. The Sparta model provides evidence about recovery that is more robust than anecdotal reports or simple counts of records. Estimates of occupancy are made at different spatial scales and compared among species and areas. Trends in occupancy are compared qualitatively with patterns in fisheries landings data. Occupancy by P. elephas has increased drastically since 2014, a pattern not seen in the other two species. For each species, occupancy varied among areas and in some areas, patterns in estimates of occupancy were similar to trends in landings from fisheries. Citizen science records are increasingly recognized to have value which has not yet been fully exploited. Greater use should be made of the Seasearch dataset in order to provide population trends for benthic marine taxa. Such analyses will broaden our understanding of and taxonomic coverage of changes in biodiversity.

The status of Asian populations of the Eurasian otter Lutra lutra is largely unknown. Since its designation as a Natural Monument (in 1983) and as Endangered (in 1997) in South Korea the authorities there have been trying to conserve and recover the species. We conducted a national otter survey by standard methods in 2017 and compared the current otter distribution to those recorded in a previous survey (2010). We found otter signs in 84.5% of 1,105 10 × 10 km grid cells, with the highest sprainting intensity in the south-west in the Yeongsan River Basin and on the south coast, where we recorded 7.05 and 6.26 spraints/site, respectively. Despite relatively low spraint densities, the otter has expanded its range since 2010 by colonizing urban areas. This trend suggests that South Korea could be a source area for the recovery of the Eurasian otter in East Asia.

We monitored egg clutch numbers of a population of the endemic Italian agile frog Rana latastei in a Site of Community Interest in northern Italy (SCI IT 209000) during 1997–2017 with the aim of assessing the long-term variation in its abundance. We walked along the banks of canals and small ponds (n = 22) 1–3 times per week between early February and mid-April each year to detect egg clutches. The relationships between the start of the breeding season, yearly egg mass counts, rate of yearly change in the number of recorded egg masses and 15 climatic and environmental variables were assessed by multiple regression. The first deposition of eggs occurred progressively later in the year throughout the study period and mean air temperature during the breeding season decreased over this period. Agile frogs showed high deposition site-fidelity. Despite large variations in the number of egg clutches detected from year to year, the population size remained stable in the long term. Peaks in the number of egg clutches occurred 2 years after the dredging of canals, carried out every 4–6 years to improve water availability, starting in 2004 as part of a LIFE Nature Project. This was the only predictor of the number of egg clutches deposited, suggesting that periodical management is needed to support the agile frog population. Our results reinforce the need for multi-year monitoring to determine both the long-term success of habitat restoration projects and the status of residual populations.

Poaching is cryptically but rapidly driving many species towards extinction. Knowledge of population trends of exploited species and incentives for poaching is necessary to inform appropriate conservation measures. We estimated the abundance of four ungulate species in Golestan National Park, Iran, the country's oldest protected area, where poaching of ungulates is widespread. We used line transect surveys (186 km), camera trapping (2,777 camera-nights), point counts (64 scans) and dung counts (along 38 km), and compared population estimates with those from earlier records. We also investigated the incentives for poaching, using a semi-structured interview survey. Population estimates for 2011–2014 indicated a 66–89% decline in three ungulate species (bezoar goat Capra aegagrus, red deer Cervus elaphus and urial Ovis vignei) compared to 1970–1978. Only wild boar Sus scrofa showed a population increase (of 58%) during the same period, possibly facilitated by religious restrictions regarding the consumption of this species. The incentives for poaching were categorized (in a non-ordinal manner) as subsistence, pleasure, tradition, trade of wild meat, and conflict with conservation regulations and bodies. The decline in hunted ungulates in this Park appears to be the result of rampant poaching, and a similar trend is evident in other protected areas in the country. We suggest the adoption of participatory conservation strategies, improvement of law enforcement practices and cooperation with international experts to reduce poaching in these protected areas. Taking into account the incentives for poaching, a combination of economic and non-economic strategies should be considered.

Trends in the populations of large herbivores in Niassa Reserve, Mozambique, have been monitored through biennial aerial surveys since 1998. The elephant Loxodonta africana population has been subjected to intensive illegal hunting since 2006. We used a simple population model to mimic the observed trends in the numbers of live and dead elephants to demonstrate the impact of poaching. The number of fresh or recent carcasses recorded was used in the model as an index of the annual mortality rate. A maximum likelihood analysis to compare population models revealed that the best fit to the survey estimates of both live elephants and old or very old carcasses was a model that started with 6,635 elephants in 1987. This number increased through births by 4.6% annually and decreased through deaths from natural and anthropogenic causes. In the best-fit model, the mean mortality rate in any year was 3.2 times the observed 1 + 2 carcass ratio (ratio for carcasses in age categories 1 and 2), and carcasses remained visible for a mean of 6 years. The model suggested that c. 900 elephants were poached during 2007–2010 and another c. 1,000 during 2011. Population estimates for live elephants and carcasses are now routine outcomes of aerial surveys conducted as part of the CITES programme for Monitoring the Illegal Killing of Elephants, and our method can be applied to any population with a time series of estimates for live and dead elephants.

The Critically Endangered tamaraw Bubalus mindorensis is endemic to Mindoro Island, Philippines, and little is known of its ecology. During 2006–2011 we used community-based monitoring to examine the population status and ecology of tamaraw in the species’ core habitat of Mount Iglit–Baco National Park. Each year, for 5 consecutive days at the end of the dry season, trained local volunteers and rangers or project staff were allocated to 18 vantage points in the study area (c. 160 km2). Tamaraw were categorized as adult (> 5 years), juvenile (2–5 years) or calf (< 2 years), and sexed when possible. During the study period the population was 239–314 (mean 271), with no significant fluctuations in age structure (percentage of adults, juveniles and calves: 57.8, 21.0 and 21.3%) or estimated adult female reproductive rates (29.1%). In adults, but not in juveniles, the sex ratio was biased towards females (1 : 1.86, P < 0.01). Bulls were often solitary (32.2% of sightings), whereas the majority of cows (94.7%) formed small groups of 2–12 individuals of different ages, with or without bulls (53.4 and 46.6%, respectively). These results demonstrate that the population remained relatively stable, maintaining a constant age structure and reproductive rate, and that long-term community-based monitoring was effective for quantitative characterization of the tamaraw's social behaviour, which is critical for conservation and management of the species.

Populations of the common hippopotamus Hippopotamus amphibius in Mozambique were surveyed in 2010 during a national survey of the crocodile Crocodylus niloticus. Numbers of hippos seen during aerial counts along major rivers and lake shores were corrected to allow for undercounting of groups and these data were supplemented with the results of other recent surveys. There are now estimated to be c. 3,000 hippos in Mozambique and c. 50% of these live in Lake Cabora Bassa or the Zambezi River. The national total is much lower than the figure of 16,000–20,500 hippos estimated in 1986, used for the latest (v. 2012.1) IUCN Red List. The 1986 total included an estimated 10,000–12,000 in Marromeu Complex, an area that includes the southern Zambezi delta. We review the results of past surveys and find that the number of hippos in Marromeu Complex in 1986 was probably three times fewer than estimated. Although the number of hippos in this area declined markedly during the 1980s we believe that the 1986 overestimate of hippos in Marromeu Complex is an error that has been perpetuated for 25 years. Particular care should be taken when Red List assessments roll-over old and unsupported estimates of numbers. Even if an old estimate was accurate there comes a time when it should not simply be rolled-over. The 2007 IUCN Species Survival Commission's African Elephant Status Report provides a model for future assessments of the status of the common hippopotamus, categorizing the numbers of a species according to the type of survey, its reliability, and how long ago it was conducted.

Until recently, the spectacled petrel Procellaria conspicillata Gould was listed as Critically Endangered due to its small population size and ongoing incidental mortality on fishing gear. Surveys at its sole breeding locality, Inaccessible Island in the central South Atlantic Ocean, indicated that the population increased from 1999–2004, resulting in the species being down-listed to Vulnerable. We repeated the census of breeding spectacled petrels during the early incubation period in October–November 2009. Numbers of burrows increased by 55% from 2004–09, with increases in all count zones, and the greatest changes in peripheral populations. Burrow occupancy estimates remained high, averaging 81% during one-off checks. Our best estimate of the population in 2009 was 14 400 pairs, continuing the c. 7% per year increase inferred since the 1930s following the disappearance of introduced pigs. This confirms the rapid recovery of this species despite ongoing mortality on fishing gear. Our results suggest that at least some procellariiforms are able to sustain strong growth rates in the face of fishing mortality when colony based threats are removed.

Several sub-Antarctic penguin populations have exhibited decreasing trends in the last 5–20 years. At Iles Kerguelen, the gentoo penguin (Pygoscelis papua) has decreased by approximately 30% over the last 15 years. This decrease is likely to be related to reduced food availability for this coastal species. We discuss this decrease with regard to the impact of overfishing and to the potential effects of climate changes on marine food webs.

A field experiment was conducted to track the daily population trends and occurrence of the flower thrips Megalurothrips sjostedti Trybom and Frankliniella occidentalis (Pergande), and their indigenous natural enemies Orius spp. and Ceranisus menes (Walker), infesting French beans. French beans in monocrop or interplanted with six companion crops (Zea mays L., Coriandrum sativum L., Tagetes erecta L., Brassica oleracea var. acephala L., Daucus carota L. and Capsicum annuum L.), and two chemical insecticides, methiocarb (Mesurol 500SC) and L-cyhalothrin (Karate 1.75% EC), were evaluated for their effects on the abundance of flower thrips, throughout the day, at 1-h intervals. The average population peak of thrips was found to occur at around 1300 h, but each species had different peak periods. Adult F. occidentalis populations peaked at midday and adult M. sjostedti populations at 1500 h, while the larvae of the two thrips species peaked at around 1300 h. Orius spp. were the most abundant natural enemies and their populations peaked at around 1400 h. Ceranisus menes population also peaked at around 1400 h.

Estimates of population size have been essential for ecological theory and wildlife management, but they depend on spatial scales of observation. Reported aspects of study and interpretive design were tested to see if they could explain variation in puma (Puma concolor) density. Comparison of puma studies revealed information shortfalls and possible confounding effects in research trends. Vegetation descriptions and other biological and physical aspects of the study site explained none of the 30-fold range of variation in puma density, nor did sampling and estimation methods and other aspects of study and interpretive design. Most (78%) of the variation in puma density estimates can be explained by the spatial extent of study area. Given the effect of scale, puma density estimates have been inappropriately extrapolated to larger geographic areas for management purposes. Due to spatial shifting of local population clusters, conventional density estimates cannot contribute to assessments of puma population trend without study at multiple sites over longer periods of time. Field studies would contribute more to knowledge of puma by spanning larger areas, a greater variety of land uses and habitats, and more of puma's range of distribution.

The Amami rabbit Pentalagus furnessi is a rare forest-dwelling form endemic to the Amami and Tokuno Islands in Japan. In order to estimate the distribution and abundance of the Amami rabbit we counted their faecal pellets along forest roads and streams as well as within the forests on Amami and Tokuno Islands during January 1993–March 1995. The number of pellets/ km along a stream gave a practical index for measuring relative abundance. The rabbit was estimated to be distributed over about 370 sq km on Amami Island and 33 sq km on Tokuno Island. There was a large variance in faecal abundance among the survey routes. Some populations were completely isolated and thought to be very small. The size of a local population was positively correlated with those of neighbouring populations and the amount of mature forest relative to other serai stages. We compared the results of this survey with those of previous surveys to find that the total population of this species appears to be declining. Some conservation measures are proposed for forest habitat management, designed to avert the decline of the Amami rabbit and to ensure its preservation.