Species’ declines are caused by a combination of factors that affect survival and/or breeding success. We studied the effects of a set of environmental and anthropogenic variables on the disappearance of Canarian Houbara Bustards Chlamydotis undulata fuertaventurae on Fuerteventura (Canary Islands), once the main stronghold of this endangered bird. Of 83 male display sites detected in 1997–1998, only 29 remained occupied in 2020–2021 (a 65% decrease in only 23 years). We compared habitat quality, density of conspecifics, other steppe birds and crows, presence of human infrastructure, and degree of environmental protection between these 29 extant sites and the 54 extinct sites using univariate analyses and generalised linear models (GLMs). The most influential variable in the abandonment of display sites was the Normalised Difference Vegetation Index (NDVI), an indicator of green vegetation productivity, which suggests a strong effect of habitat aridification due to climate change on the population’s extinction process. Powerline density was the second most important factor. This suggests that houbaras have survived where a greater abundance of food resources has enabled a higher breeding success, and where powerline fatalities have caused lower mortality over the years. Higher densities of houbaras, and other steppe birds and crows at extant display sites confirmed the better habitat quality in these areas. Extant display sites, located generally in protected areas, also had lower densities of human infrastructure (e.g. buildings, roads). We discuss the conservation implications of these results and provide management recommendations for this endangered subspecies.

The Secretarybird Sagittarius serpentarius is a charismatic raptor of the grasslands and open savannas of Africa. Evidence of widespread declines across the continent has led to the assessment that the species is at risk of becoming extinct. Southern Africa was identified as a remaining stronghold for the species, but the status of this population requires reassessment. To determine the status of the species in South Africa, Lesotho, and Eswatini, we analysed data from a citizen science project, the Southern African Bird Atlas Project (SABAP). We implemented novel time-to-detection modelling, as well as summarisation of changes in reporting rates, using standard metrics, to determine the trajectory of the population. To cross-validate our findings, we used data from another citizen science project, the Coordinated Avifaunal Roadcounts (CAR) project. While our results were in agreement with previous studies that have reported significant declines when comparing SABAP1 (1987–1992) and SABAP2 (2007 and onwards), all analysis pathways that examined data within the SABAP2 period only, as well as CAR data from this period, failed to show an alarming declining trend over this more recent time period. We did, however, find some evidence for decreases in Secretarybird abundance in urban grid cells. We used random forest models to predict probability of occurrence, as well as probability of abundance (reporting rates) for the assessed region and provided population estimates based on these analysis pathways. Continued monitoring and conservation efforts are required to guard this population stronghold.

Despite significant research, the direct and indirect causes of a population decline in the eponymous foragers of the Late Jōmon period (c. 4500–2300 BP) in Japan remains undetermined. Here, the authors examine the impact of nutritional stress, using scurvy as a case study, on Middle and a Late/Final Jōmon populations. While an increase in the prevalence of scurvy between the time periods is apparent, no associated change in age at death was observed. The authors argue that the Late Jōmon adapted their food-sharing practices in times of ecological stress, and they highlight the need to consider morbidity and mortality together in palaeopathological assessments and the growing evidence for a non-nutritional cause in the Late Jōmon population decline.

Across South Africa, Lesotho, and Eswatini, long-term citizen science atlas data have suggested concerning declines in the population of Black Stork Ciconia nigra. Unlike the Asian and European populations, the southern African Black Stork population is described as resident and is listed as “Vulnerable” in South Africa, Lesotho, and Eswatini. Here we report on surveys of historical nesting locations across northern South Africa, finding evidence for nest site abandonment and limited evidence of recent breeding. We undertook detailed species distribution modelling within a maximum entropy framework, using occurrence records from the BirdLasser mobile app. We cross-validated the models against information in the Southern African Bird Atlas Project (SABAP2) database, highlighting Lesotho as an important potential breeding area. Additionally, we used SABAP2 to assess population trends by investigating interannual patterns in reporting rate. Comparing current reporting rates with those from SABAP1 (1987–1992), we found that there has been a dramatic decrease. We noted that a large proportion of the population occurs outside the breeding range during the breeding season, suggesting a considerable non-breeding population, especially in the extensive wildlife refuge of the Kruger National Park. The slow declines observed might be indicative of a population which is not losing many adults but is failing to recruit significant numbers of juveniles due to limited breeding. Using densities derived from transect surveys, we used predictive models to derive estimates of breeding range carrying capacity and a population estimate, which suggested declines to numbers around 600 for this subregion. Minimising disturbance at breeding sites of this cliff-nesting species and improving water quality at key population strongholds are pathways to improving the status of the species in the subregion.

We describe the population of the Еndangered sea otter Enhydra lutris on Urup Island, one of the main wildlife refuges in the southern Kuril Islands of Russia. We reviewed historical and local reports of the sea otter, identified its habitat around the island, and surveyed the coastal waters of the island in 2019. Sea otters were numerous on Urup Island in the past but were hunted excessively and almost exterminated by the 1950s. Since then, sea otter populations have increased, and as the island is almost uninhabited we expected otters to be numerous. This was not the case, and we estimated the total population to be 363 ± SE 126 individuals. Our observation of two skinned carcasses on the shore suggests the low numbers are a result of poaching for the illegal fur trade. The case of Urup Island demonstrates that sea otters require active conservation, as even on a remote island they remain threatened. Establishment of protected areas would be an effective conservation measure for this species, although the suppression of demand for sea otter fur is of the greatest importance.

Over recent decades, Chinese giant salamanders Andrias spp. have declined dramatically across much of their range. Overexploitation and habitat degradation have been widely cited as the cause of these declines. To investigate the relative contribution of each of these factors in driving the declines, we carried out standardized ecological and questionnaire surveys at 98 sites across the range of giant salamanders in China. We did not find any statistically significant differences between water parameters (temperature, dissolved oxygen, ammonia, nitrite, nitrate, salinity, alkalinity, hardness and flow rate) recorded at sites where giant salamanders were detected by survey teams and/or had been recently seen by local respondents, and sites where they were not detected and/or from which they had recently been extirpated. Additionally, we found direct and indirect evidence that the extraction of giant salamanders from the wild is ongoing, including within protected areas. Our results support the hypothesis that the decline of giant salamanders across China has been primarily driven by overexploitation. Data on water parameters may be informative for the establishment of conservation breeding programmes, an initiative recommended for the conservation of these species.

Public preferences for wildlife protection can dictate the success or failure of conservation interventions. However, little research has focused on wildlife preferences among youth or how youth prioritize species-based conservation. We conducted a study of youth between 7 and 20 years old (n = 128) at five local schools situated near critical hawksbill turtle (Eretmochelys imbricata) nesting beaches in El Salvador to determine their wildlife preferences and how they prioritize species for conservation based on five attributes: endemism; use for hunting and fishing; rapid decline in population size; presence around their home; and ecological significance. These Salvadoran youth showed preferences for native over non-native species and tended to rank rapid population decline as the most important attribute for prioritizing wildlife for protection, followed by use for hunting and fishing. Participants in local environmental education activities placed greater importance on species in rapid decline than non-participants, who considered endemism as most important. Overall, these findings reveal how environmental education may successfully promote increased prioritization of imperilled species among youth. Economic payments for conserving hawksbill turtles may link the two top reasons that Salvadoran youth provided for protecting species by compensating for the reduced hunting required to facilitate population stabilization.

The endemic Galapagos Martin Progne modesta is a rare species. Population sizes in the past are unknown, but the few reports available suggest that it has become rarer in some sites. To obtain a better understanding of its population status, a simultaneous survey was conducted in 2017 around the coastline of 14 islands and 23 islets resulting in sightings of only 26 individuals. A simultaneous survey on Sierra Negra volcano on Isabela Island added five more individuals. However, observations from early expeditions and expeditions since 2015 have shown that the volcanoes of Isabela Island are important feeding areas and probable breeding areas for the Galapagos Martin, but these were largely excluded from the survey in 2017 due to logistical reasons. Historical and recent nesting sites include Tagus Cove on Isabela Island and Daphne Major Island. During our 2017 count, three possible new nesting sites were discovered: Daphne Minor, Santiago and a small crater on Punta Cristóbal on southwestern Isabela Island. From 2015 to 2018, 15 nests were also observed on the cliff in Tagus Cove. Two accessible nests were collected and revealed the first records of Philornis downsi in Galapagos Martin nests. The impact of parasitism by P. downsi is unknown but potentially severe. Given the lack of general knowledge about the biology of this species and its apparent low population sizes, further studies are urgently needed.

The Parc National du Banc d’Arguin in Mauritania hosts the largest concentrations of coastal waterbirds along the East Atlantic Flyway. In spite of this importance, a review of the changes in the numbers of waterbirds in the area is lacking since the first complete count in 1980. Here we analysed the seven complete waterbird counts made since then, and the additional yearly counts made in one subunit (Iwik region) since 2003. We present evidence for changes in the community composition of waterbirds over the past four decades. Total waterbird numbers showed a decrease between 1980 and 2017, with only Great White Pelican Pelecanus onocrotalus showing a significant increase in numbers. Five species showed significant declines: Long-tailed Cormorant Phalacrocorax africanus, Red Knot Calidris canutus, Bar-tailed Godwit Limosa lapponica, Eurasian Curlew Numenius arquata, and Western Marsh Harrier Circus aeruginosus. In the remaining species, the variation in numbers between counts was too large, and the number of complete counts too small, for trends to be detected. The yearly counts at Iwik region also showed sharp decreases in the numbers of Red Knot, Bar-tailed Godwit, and Marsh Harrier, but not of Long-tailed Cormorant and Eurasian Curlew. A multivariate analysis revealed a significant change in species composition over time, which was caused mainly by changes in the species depending on the intertidal mudflats for feeding (generally in decline) vs. the species depending on fish and crustaceans in the sublittoral and offshore zones (often showing increases).

A dramatic reduction in catch rates of Antarctic toothfish in McMurdo Sound, Antarctica, has led to conclusions that the commercial bottom longline fishery for toothfish in the Ross Sea has drastically altered the toothfish population with cascading effects on the McMurdo Sound ecosystem. However, results from a new monitoring programme for Antarctic toothfish and other top predators carried out in McMurdo Sound in 2014 have shown toothfish catch rate, fish size and fish age similar to those observed prior to 2002. These results suggest that either large and old fish have returned to McMurdo Sound following a temporary environmentally driven absence or that they remained locally present but were not detected in the areas sampled. These findings highlight the importance of continued standardized monitoring for detecting the potential effects of fishing on the Ross Sea ecosystem.

Citizen science monitoring programmes are making increasingly important contributions to wildlife conservation, often at spatial and temporal scales unachievable by individual or teams of researchers. They are particularly valuable in estimating population trends and management impacts, and thus informing effective conservation decisions for declining species. The quality and potential biases of citizen science data are of concern, however, and appropriate experimental design and analysis are needed to ensure that the maximum scientific value is extracted. We investigated these issues in a citizen science survey of the Endangered Carnaby's black-cockatoo Calyptorhynchus latirostris. Since 2010, citizen scientists have conducted synchronized annual counts of Carnaby's black-cockatoo at roost sites to estimate the population trend. Survey effort was substantial, with c. 150 sites surveyed by > 260 volunteers each year. Relatively few sites were occupied, however, and only 42 (16%) of the 265 sites surveyed in total accounted for 95% of all observations. Many sites were empty and survey effort was often inconsistent. Taking these issues into account, analysis showed a statistically significant decline in roost occupancy rate and a non-significant decline in the mean size of roosting flocks, with an estimated overall trend of 14% decline per annum in the number of roosting birds. We highlight three important issues for citizen science monitoring programmes: the need to maintain regular surveys of sample sites to avoid patchy data, use an appropriate model that accounts for variable survey effort, high frequency of zero counts, and sampling site turnover, and incorporate information on site characteristics to help explain variation.

The Adélie penguin (Pygoscelis adeliae) breeding population at Stranger Point, King George Island (25 de Mayo), increased in number from 1965/66 until 1980/81 after which it started to decrease almost continuously up to the present. A significant decrease in the number of breeding pairs and chicks crèched was observed between 1995/96 and 2013/14 (75% and 78%, respectively), although the rate of this decrease has slowed since 2006/07. Over the last seven years, larger interannual fluctuations were recorded in the number of breeding pairs and chicks in crèches, as well in the breeding success. The values for the index of breeding success during 2007/08, 2009/10 and 2012/13 were low and this parameter showed higher temporal fluctuation in the period 2007/08 to 2013/14. The reduction in breeding success and the number of chicks reared to crèche will unfavourably impact on future population size at Stranger Point through the reduction of new recruits. Although Adélie penguin population trends on the Antarctic Peninsula are linked to the marine environment variability (i.e. reduction in sea ice affecting the availability of prey), breeding success is also influenced by the amount of snow fall which has increased in recent years.

We report changes in guanaco Lama guanicoe density, recruitment, and social structure associated with increased access of poachers along an extensive network of hydrocarbon-exploration roads in northern Patagonia, and conservation measures taken in response. Mean guanaco densities declined 93–96% and mean group size declined from 9.8 to 5.0 guanacos per group at three sites surveyed during 1982–1983 and 2002–2007, whereas yearling proportions did not change significantly. Additional surveys during 2002–2007 suggest population declines and fragmentation have occurred over a wide area of intense hydrocarbon exploration and extraction. Guanaco densities in 2002–2007 showed a strong negative association with the density of access points along hydrocarbon-exploration roads and, to a lesser degree, with livestock densities. The increase in poaching in recent decades, resulting from increased access and an urban population that has appropriate vehicles, has probably been the main cause of the decline of the guanaco population, although overgrazing by livestock and decreased plant productivity may also be contributing factors. Closing of exploration roads with levees and ditches in 2006 and 2010 by a hydrocarbon company, under supervision by the local government and scientists, restricted access by unauthorized vehicles to a 220,000-ha area, including two of the sites where guanaco numbers collapsed. This action, in combination with increased ranger patrols, may allow guanaco recovery in the coming years.

The woylie Bettongia penicillata is categorized as Critically Endangered, having declined by c. 90% between 1999 and 2006. The decline continues and the cause is not fully understood. Within a decline diagnosis framework we characterized the nature of the decline and identified potential causes, with a focus on the species’ largest populations, located in south-west Western Australia. We described the spatio-temporal pattern of the decline, and several attributes that are common across sites. We categorized the potential causes of the decline as resources, predators, disease and direct human interference. Based on the available evidence the leading hypothesis is that disease may be making woylies more vulnerable to predation but this remains to be tested. No substantial recoveries have been sustained to date, and one of the three remaining indigenous populations now appears to be extinct. Therefore, verifying the factors causing the decline and those limiting recovery is becoming increasingly urgent. Active adaptive management can be used to test putative agents, such as introduced predators. Insurance populations and ecological monitoring should also be included in an integrated conservation and management strategy for the species.

An assemblage of killer whales that has been sighted in waters off the west coast of the British Isles and Ireland has previously been shown to be isolated from other North Atlantic killer whale communities based on association patterns. By applying a Bayesian formulation of the Jolly–Seber mark-recapture model to the photo-identification data compiled from opportunistic photographic encounters with this population of killer whales, we show that such sparse and opportunistically-collected data can still be valuable in estimating population dynamics of small, wide-ranging groups. Good quality photo-identification data was collected from 32 encounters over 19 years. Despite a cumulative total of 77 identifications from these encounters, just ten individuals were identified and the remaining 67 identifications were re-sights of these ten animals. There was no detected recruitment through births during the study and, as a result, the population appears to be in a slight decline. The demography of the population was highly skewed towards older individuals and had an unusually high ratio of adult males, and we suggest that demographic stochasticity due to a small population size may be further impacting the population growth rate. We recommend that this population be managed as a separate conservation unit from neighbouring killer whale populations.

The historical deforestation of the Upper Brahmaputra Valley in the Indian state of Assam has resulted in the transformation of its once-contiguous lowland rainforests into many isolated forest fragments that are still rich in species, including primates. We report the recent history and current status of six diurnal primates in one large (2,098 ha) and three small (<500 ha) fragments of the Upper Brahmaputra Valley. We censused primates in the small fragments during 2002, 2005, 2009, in the large fragment in 2008, and used other published census data to derive population trends. We also used key informant surveys to obtain historical occurrence data for these populations. Our analyses reveal the recent extinction of some populations and the simultaneous long-term persistence of others in these fragments over 16 years. Most populations appeared to have declined in the small fragments but primate abundance has increased significantly in the largest fragment over the last decade. Addressing the biomass needs of the local human populations, which appears to drive habitat degradation, and better protection of these forests, will be crucial in ensuring the future survival of this diverse and unique primate assemblage in the last rainforest fragments of the human-dominated Upper Brahmaputra Valley.

The brush-tailed bettong (Bettongia penicillata), or woylie, is a medium-sized macropod marsupial that has undergone a rapid and substantial decline throughout its home range in the Upper Warren region of Western Australia over a period of approximately 5 years. As part of an investigation into possible causes of the decline a morphologically distinct Trypanosoma sp. was discovered by light microscopy in the declining population but was absent in a stable population within the Karakamia Wildlife Sanctuary. Further investigations employing molecular methods targeting variations in the 18s rRNA gene determined that the trypanosome was novel and was also present within the Karakamia population albeit at a much lower overall prevalence and individual parasitaemia levels. Phylogenetic analysis suggests the novel Trypanosoma sp. to be closely related to other trypanosomes isolated from native Australian wildlife species. Although it appears unlikely that the parasite is solely responsible for the decline in woylie population size, it may (singularly or in conjunction with other infectious agents) predispose woylies to increased mortality.