Immunity and parasites have been linked to the success of invasive species. Especially lower parasite burden in invasive populations has been suggested to enable a general downregulation of immune ...investment (Enemy Release and Evolution of Increased Competitive Ability Hypotheses). Simultaneously, keeping high immune competence towards potentially newly acquired parasites in the invasive range is essential to allow population growth. To investigate the variation of immune effectors of invasive species, we compared the mean and variance of multiple immune effectors in the context of parasite prevalence in an invasive and a native Egyptian goose (Alopochen aegyptiacus) population. Three of ten immune effectors measured showed higher variance in the invasive population. Mean levels were higher in the invasive population for three effectors but lower for eosinophil granulocytes. Parasite prevalence depended on the parasite taxa investigated. We suggest that variation of specific immune effectors, which may be important for invasion success, may lead to higher variance and enable invasive species to reduce the overall physiological cost of immunity while maintaining the ability to efficiently defend against novel parasites encountered.
Technological advances such as camera traps, and citizen science, coupled with advanced quantitative approaches, can help fill existing knowledge gaps and aid effective conservation.
We combine ...citizen and camera trap observations to estimate survival of the Endangered lappet-faced vulture, assess the relative contribution of data from camera traps and citizens, as well as impact of loss of individual marks (wing tags), on survival estimates.
We used data from 762 lappet-faced vultures wing tagged as nestlings during 2006–2017 in western Namibia. Observations of wing tagged individuals were provided by citizens or via camera traps. We formulated a multievent capture-mark-recapture model to estimate survival while accounting for probabilities of resighting by citizens and/or camera traps, recovery of dead individuals, and loss of the wing tag.
Survival was relatively high for juveniles (0.79), and increased with age to 0.95. Citizen observations of live and dead birds were low in number. However, when combined with camera trap resightings of live individuals, citizen observations increased the precision of survival estimates of birds older than one year compared to using data from either sources separately. Wing tag loss was high after 5–6 years of tag age. If neglected, tag loss can result in severe underestimation of survival of the older age classes.
Overall, we show that filling ecological knowledge gaps is possible through the efficient use of data provided by different sources, and by applying state-of the art approaches that minimise potential biases, such as those due to tag loss.
•Demographic parameters are unknown for many endangered species•We quantify survival of an endangered vulture in Southern Africa.•Information from camera traps and citizens proved critical to estimate survival.•Survival of juveniles and adults is high (0.80 up to 0.95, respectively).•Loss of wing tags, if not accounted for, biases adult survival.•Advanced methods are necessary for unbiased survival estimates.
Many long‐distance migrating shorebird (i.e., sandpipers, plovers, flamingos, oystercatchers) populations are declining. Although regular shorebird monitoring programs exist worldwide, most estimates ...of shorebird population trends and sizes are poor or nonexistent. We built a state‐space model to estimate shorebird population trends. Compared with more commonly used methods of trend estimation, state‐space models are more mechanistic, allow for the separation of observation and state process, and can easily accommodate multivariate time series and nonlinear trends. We fitted the model to count data collected from 1990 to 2013 on 18 common shorebirds at the 2 largest coastal wetlands in southern Africa, Sandwich Harbour (a relatively pristine bay) and Walvis Bay (an international harbor), Namibia. Four of the 12 long‐distance migrant species declined since 1990: Ruddy Turnstone (Arenaria interpres), Little Stint (Calidris minuta), Common Ringed Plover (Charadrius hiaticula), and Red Knot (Calidris canutus). Populations of resident species and short‐distance migrants increased or were stable. Similar patterns at a key South African wetland suggest that shorebird populations migrating to southern Africa are declining in line with the global decline, but local conditions in southern Africa's largest wetlands are not contributing to these declines. State‐space models provide estimates of population levels and trends and could be used widely to improve the current state of water bird estimates.
Protected areas are intended as tools in reducing threats to wildlife and preserving habitat for their long-term population persistence. Studies on ranging behavior provide insight into the utility ...of protected areas. Vultures are one of the fastest declining groups of birds globally and are popular subjects for telemetry studies, but continent-wide studies are lacking. To address how vultures use space and identify the areas and location of possible vulture safe zones, we assess home range size and their overlap with protected areas by species, age, breeding status, season, and region using a large continent-wide telemetry datasets that includes 163 individuals of three species of threatened Gyps vulture. Immature vultures of all three species had larger home ranges and used a greater area outside of protected areas than breeding and non-breeding adults. Cape vultures had the smallest home range sizes and the lowest level of overlap with protected areas. Rüppell's vultures had larger home range sizes in the wet season, when poisoning may increase due to human-carnivore conflict. Overall, our study suggests challenges for the creation of Vulture Safe Zones to protect African vultures. At a minimum, areas of 24,000 km2 would be needed to protect the entire range of an adult African White-backed vulture and areas of more than 75,000 km2 for wider-ranging Rüppell's vultures. Vulture Safe Zones in Africa would generally need to be larger than existing protected areas, which would require widespread conservation activities outside of protected areas to be successful.
Although communal goods are often critical to society, they are simultaneously susceptible to exploitation and are evolutionarily stable only if mechanisms exist to curtail exploitation. Mechanisms ...such as punishment and kin selection have been offered as general explanations for how communal resources can be maintained. Evidence for these mechanisms comes largely from humans and social insects, leaving their generality in question. To assess how communal resources are maintained, we observed cooperative nest construction in sociable weavers (Philetairus socius). The communal nest of sociable weavers provides thermal benefits for all individuals but requires continual maintenance. We observed cooperative nest construction and also recorded basic morphological characteristics. We also collected blood samples, performed next-generation sequencing, and isolated 2358 variable single nucleotide polymorphisms (SNPs) to estimate relatedness. We find that relatedness predicts investment in cooperative nest construction, while no other morphological characters significantly explain cooperative output. We argue that indirect benefits are a critical fitness component for maintaining the cooperative behavior that maintains the communal good.
The Orange River mouth (ORM), at the end of the longest river in South Africa, is one of few perennial wetlands on the arid south-west African coast. The ORM supports a large number of waterbirds, ...with a maximum of 20 653-26 653 individuals of 57 species being recorded in December 1985. Because of its importance for waterbirds, the ORM is recognised as a Ramsar site and an Important Bird Area. Since being designated a Ramsar site in 1991, however, the number of waterbirds has decreased (by c. 74% since the first two surveys in 1980 and 1985). During 13 surveys conducted from December 1995 to August 2001 an average of 6 873 (±1 719 SD; n = 6) and 5 547 (±2 039 SD; n = 7) individuals were recorded during summer and winter, respectively. This decrease, in conjunction with the degradation of the c. 300ha saltmarsh resulted in the ORM being placed on the Ramsar Convention's Montreux Record in 1995. The decrease in the number of waterbirds at the ORM is mainly attributable to the absence of large numbers of Cape Cormorants (Phalacrocorax carbo) and non-breeding Common Terns (Sterna hirundo), with no breeding of the former being recorded on islands in the mouth area after 1993. The decrease in numbers of these two species may be attributed to both on- and off-site factors. During a re-evaluation of the revised Ramsar criteria, we found that the site still meets three of the four Ramsar criteria under which it was originally designated in 1991 and five of the eight new criteria. The establishment of a transboundary statutory protected area will allow for the implementation of conservation-directed management measures. We propose various management recommendations to improve the conservation of wetland birds at the ORM.
Although Namibia is considered to be a largely arid country, it does support a wide range of wetland habitats, including ephemeral water bodies and pools of rainwater, artesian springs that support ...small perennial pools and streams, and large rivers in the northeastern section of the country. Rivers in this region drain areas north of Namibia that receive much more rainfall, and contribute most of the tropical species found in Namibia's wetlands. Researchers have identified 778 species of macro-invertebrates in Namibia's wetlands. The greatest levels of endemism occur among Ostracoda, Coleoptera, Diptera, Anostraca, and Amphipoda. An estimated 50 species of frogs live in Namibia, with three species endemic to the region. In addition, 114 species of freshwater fish have been identified in the region.
Namibia is an arid country but has a diverse array of wetland habitats ranging from ephemeral water bodies and rain-pools, artesian springs supporting small perennial pools and streams, to the large ...perennial rivers of the north-east with their associated floodplains. These rivers drain wetter areas north of Namibia and contribute many tropical species to Namibia's wetlands. There are 778 described species of macro-invertebrates representing eight phyla with 81 endemics. Many invertebrates still have to be identified or described but presently the greatest endemism occurs among the Ostracoda (18 species), Coleoptera (17), Diptera (14), Anostraca (six) and Amphipoda (five species). In total, Namibia has 50 species of frog with three endemics. No caecilians or salamanders occur in Namibia. There are 114 species of freshwater fish with five endemics. Most Namibian wetlands occur outside protected areas. Over-exploitation of wetland resources and flow regulation are currently major threats, but new environmental legislation being formulated is based on the goal of sustainable use.PUBLICATION ABSTRACT
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