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Vultures (Accipitridae and Cathartidae) are the only known obligate scavengers. They feed on rotting carcasses and are the most threatened avian functional group in the world. Possible effects of vulture declines include longer persistence of carcasses and increasing abundance of and contact between facultative scavengers at these carcasses. These changes could increase rates of transmission of infectious diseases, with carcasses serving as hubs of infection. To evaluate these possibilities, we conducted a series of observations and experimental tests of the effects of vulture extirpation on decomposition rates of livestock carcasses and mammalian scavengers in Kenya. We examined whether the absence of vultures changed carcass decomposition time, number of mammalian scavengers visiting carcasses, time spent by mammals at carcasses, and potential for disease transmission at carcasses (measured by changes in intraspecific contact rates). In the absence of vultures, mean carcass decomposition rates nearly tripled. Furthermore, the mean number of mammals at carcasses increased 3-fold (from 1.5 to 4.4 individuals/carcass), and the average time spent by mammals at carcasses increased almost 3-fold (from 55 min to 143 min). There was a nearly 3-fold increase in the mean number of contacts between mammalian scavengers at carcasses without vultures. These results highlight the role of vultures in carcass decomposition and level of contact among mammalian scavengers. In combination, our findings lead us to hypothesize that changes in vulture abundance may affect patterns of disease transmission among mammalian carnivores. Los buitres (Accipitridae y Cathartidae) son los únicos carroñeros obligados que se conocen. Se alimentan de cadáveres en descomposición y son el grupo funcional de aves más amenazado del mundo. Los efectos posibles de las declinaciones de buitres incluyen una mayor persistencia de cadáveres y el incremento de la abundancia de y contacto entre carroñeros facultativos en esos cadáveres. Estos cambios podrían incrementar las tasas de transmisión de enfermedades infecciosas, con los cadáveres funcionando como focos de infección. Para evaluar estas posibilidades, realizamos una serie de observaciones y pruebas experimentales de los efectos de la extirpación de buitres sobre las tasas de descomposición de cadáveres de ganado y mamíferos carroñeros en Kenia. Examinamos sí la ausencia de buitres cambiaba el tiempo de descomposición de cadáveres, el número de mamíferos carroñeros visitando los cadáveres, el tiempo utilizado por mamíferos en los cadáveres y la potencial transmisión de enfermedades en los cadáveres (medida por cambios en las tasas de contacto interespecífico). En ausencia de buitres, las tasas medias de descomposición de cadáveres incrementaron 3 veces (de 1.5 a 4.4 individuos/cadáver), y el tiempo promedio invertido por mamíferos en los cadáveres incrementó casi 3 veces (de 55 min a 143 min). Hubo un aumento de casi tres veces en el número promedio de contactos entre mamíferos carroñeros en cadáveres sin buitres. Estos resultados resaltan el papel de los buitres en la descomposición de cadáveres y del nivel de contacto entre mamíferos carroñeros. En combinación, nuestros resultados nos llevaron a plantear la hipótesis de que cambios en la abundancia de buitre pueden afectar los patrones de transmisión de enfermedades entre mamíferos carnívoros.

At-sea mortality information is important for understanding the magnitude of threats to protected sea turtle species. When a sea turtle dies, it typically sinks, starts decomposing, and will eventually float to the surface if the carcass remains intact and enough internal gases accumulate. However, few data are available regarding the rate and duration of these processes to allow estimation of time since death once carcasses are recovered. Twenty-seven Kemp's ridley (Lepidochelys kempii) and 15 green (Chelonia mydas) sea turtle cold-stunned carcasses were placed in wire mesh, weighted cages at varying water depths (10–40 m) and temperatures (18.5°C–28.7°C) in the northern Gulf of Mexico from June 2018 to October 2019. Cameras and temperature-depth-orientation recorders were used to document decomposition progression and carcass buoyancy. Decomposition rate was measured using corrected accumulated degree hours and values of observed time-to-float were compared with predictions based on laboratory and field experiments in previous research. Overall, carcasses did not float when deployed in waters > 30 m when temperatures were < 22°C and carcasses tended to float sooner in ≤ 20 m depths, especially if bottom temperatures were > 24°C. Green sea turtle carcasses floated in a variety of environmental conditions, but onset of positive buoyancy was not very predictable. Buoyancy of Kemp's ridley sea turtle carcasses was inconsistent, but float times were fairly predictable. We did not identify the exact depth at which sea turtle carcasses cannot generate enough gases to float, but that depth is likely very close to 40 m. Carcasses that became buoyant in ≥ 30 m depths tended to float for < 24 hrs before sinking again and, therefore, it is unlikely that they have enough time to drift to shore. This information enhances our understanding of the likelihood of carcasses washing ashore and can be incorporated into carcass backtracking analyses to facilitate identification of mortality causes.

Scavenging mammals and vultures can exploit and deplete carcasses much faster than other birds and invertebrates. Vultures are strongly influenced by habitat type, e.g. tree cover, since they rely on their eyesight to detect carcasses. It remains unclear whether and how facultative scavengers – both other birds and mammals – are influenced by tree cover and how that affect carcass decomposition time, which in turn affects biodiversity and ecological processes, including the cycle of energy and nutrients. We studied whether the carcass detection and consumption, hence carcass decomposition speed, by facultative avian and mammalian scavengers varies with tree cover in areas without vultures. Fresh mammal carcasses were placed in different landscapes across the Netherlands at locations that widely varied in tree cover. Camera traps were used to record carcass exploitation by facultative avian and mammalian scavengers and to estimate carcass decomposition time. We found that carcass detection and consumption by birds, wild boar, and other mammals varied between locations. Carcass decomposition speed indeed increased with carcass detection and exploitation by mammals, especially by wild boar. However, this variation was not related to tree cover. We conclude that tree cover is not a major determinant of carcass exploitation by facultative scavengers in areas without obligate scavengers and large carnivores. We studied whether the carcass detection and consumption, hence carcass decomposition speed, by facultative avian and mammalian scavengers varies with tree cover in areas without vultures. Carcass decomposition speed indeed increased with carcass detection and exploitation by mammals, especially by wild boar. However, this variation was not related to tree cover.

Carcass decomposition largely depends on vertebrate scavengers. However, how behavioral differences between vertebrate scavenger species, the dominance of certain species, and the diversity of the vertebrate scavenger community affect the speed of carcass decomposition is poorly understood. As scavenging is an overlooked trophic interaction, studying the different functional roles of vertebrate species in the scavenging process increases our understanding about the effect of the vertebrate scavenger community on carcass decomposition. We used motion‐triggered infrared camera trap footages to profile the behavior and activity of vertebrate scavengers visiting carcasses in Dutch nature areas. We grouped vertebrate scavengers with similar functional roles. We found a clear distinction between occasional scavengers and more specialized scavengers, and we found wild boar (Sus scrofa) to be the dominant scavenger species in our study system. We showed that these groups are functionally different within the scavenger community. We found that overall vertebrate scavenger diversity was positively correlated with carcass decomposition speed. With these findings, our study contributes to the understanding about the different functional roles scavengers can have in ecological communities. We examined functional differences within the scavenger community and found groups of scavengers with similar roles. Wild boar (Sus scrofa) was determined to be the dominant scavenger in our system, accelerating the carcass decomposition speed.

Stranded sea turtles provide valuable information about causes of mortality that threatens these imperiled species. Many potential factors determine whether drifting sea turtles are deposited on shore, discovered by people, and reported to stranding networks resulting in successful documentation. We deployed 182 sea turtle cadavers and 115 wooden effigy drifters with affixed GPS-satellite tags to study stranding probability in the northern Gulf of Mexico (nGOM) in an effort to better understand seasonal stranding variations in this region. Public reports of beached carcasses were recorded to determine reporting rates. Season and distance from shore greatly influenced beaching results. During winter months when strandings are infrequent and sea turtle abundance is likely low in cold nearshore waters, carcasses had an 80–90% probability of beaching. Beaching probability was reduced to 37–50% during the spring, which is the period of greatest strandings in this region. During summer months when relatively few strandings are documented, the probability of a carcass beaching dropped to only 4–8%. Low summer stranding rates were coincident with higher rates of decomposition (7%) attributed to warmer water temperatures, more frequent scavenging (69% of carcasses), and shifting wind and current patterns which drive carcasses offshore or to remote locations. As waters cooled in the fall, probability of carcasses beaching increased to 40–48%, coincident with a small pulse in strandings that often occurs during this period. Only 28% of carcasses and effigies came ashore on mainland beaches and were easily available for discovery by the public, 49% were on barrier islands that are publicly accessible and 23% beached in dense salt marshes where discovery would be unlikely. The 47% of objects that did not beach included those lost at sea and carcasses that were likely scavenged or decomposed. Only 22% of beached carcasses were reported due to infrequent (11%) reporting on barrier islands. Notably, only 50% of carcasses deposited on mainland beaches were reported, which was lower than anticipated. We recommend additional efforts to increase reporting rates of carcasses by the public and use of dedicated surveys to detect stranded sea turtles, especially on barrier islands in this region.

The decay process of animal carcasses is a highly complex succession driven by abiotic and biotic variables and their interactions. As an underexplored ecological recycling process, understanding carrion decomposition associated with pandemics such as African swine fever is important for predicting the rate and post‐mortem interval (PMI) variation of wild animal carcasses to improve disease management. To model PMIs of wild boar, we deployed 73 wild boar carcasses in four different forest habitat types throughout a year and monitored the decomposition process, carrion beetles and blow fly larval populations. The 601 single observations were split randomly into 501 training data and 100 validation data. A linear additive mixed model for log‐transformed PMI values using the training data identified the decay stage, day of year, ambient temperature during sampling, habitat and prevalence of Oiceoptoma thoracicum (Silphidae) as predictive variables for time since death, but neither the initial body mass nor if a fresh or previous frozen carcass was used. Using the validation data, this model showed a high predictive power for log‐transformed PMI values (R2 = 0.80). This study aimed at improving the methodology of estimating the PMI of wild boar carcasses based on important abiotic and biotic environmental factors that can be easily assessed in the field. Using only a small set of predictors, including a conspicuous beetle species, allowed prediction of the mean, minimum and maximum PMI of wild boar carcasses. The strong effects of a few surrogates on PMI in our model suggest that this model can easily be transferred to wider regions of Central Europe by retraining the model with data from a broader environmental space and can thus be instrumental in assessing timing of disease introduction in areas newly affected by emerging diseases such as African swine fever. Validation of a model to predict the time since death using 501 training data and 100 independent randomly selected validation values. Insets show a carrion beetle supporting the model and a wild boar at late decay stage.

Background The pulsed introduction of dead plant and animal material into soils represents one of the primary mechanisms for returning organic carbon (C) and nitrogen (N) compounds to biogeochemical cycles. Decomposition of animal carcasses provides a high C and N resource that stimulates indigenous environmental microbial communities and introduces non-indigenous, carcass-derived microbes to the environment. However, the dynamics of the coalesced microbial communities, and the relative contributions of environment- and carcass-derived microbes to C and N cycling are unknown. To test whether environment-derived, carcass-derived, or the combined microbial communities exhibited a greater influence on C and N cycling, we conducted controlled laboratory experiments that combined carcass decomposition fluids and soils to simulate carcass decomposition hotspots. We selectively sterilized the decomposition fluid and/or soil to remove microbial communities and create different combinations of environment- and carcass-derived communities and incubated the treatments under three temperatures (10, 20, and 30 °C). Results Carcass-derived bacteria persisted in soils in our simulated decomposition scenarios, albeit at low abundances. Mixed communities had higher respiration rates at 10 and 30 °C compared to soil or carcass communities alone. Interestingly, at higher temperatures, mixed communities had reduced diversity, but higher respiration, suggesting functional redundancy. Mixed communities treatments also provided evidence that carcass-associated microbes may be contributing to ammonification and denitrification, but that nitrification is still primarily carried out by native soil organisms. Conclusions Our work yields insight into the dynamics of microbial communities that are coalescing during carcass decomposition, and how they contribute to recycling carcasses in terrestrial ecosystems.

Bromadiolone is a second generation anticoagulant rodenticide (SGAR) used to control pest rodents worldwide. SGARs are frequently involved in secondary poisoning in rodent predators due to their persistence and toxicity. This study aims to evaluate the persistence of bromadiolone in liver at different stages of carcass decomposition in experimentally-dosed common kestrels ( ) to understand the possibility of detecting bromadiolone in cases of wildlife poisoning and the potential risk of tertiary poisoning. Twelve individuals were divided into the bromadiolone-dose group (dosed with 55 mg/kg b.w) and the control group. Hepatic bromadiolone concentrations found in each stage of decomposition were: 3000, 2891, 4804, 4245, 8848, and 756 ng/g dry weight at 1-2 h (fresh carcass), 24 h (moderate decomposition), 72 h, 96 h (advanced decomposition), seven days (very advanced decomposition), and 15 days (initial skeletal reduction) after death, respectively. Liver bromadiolone concentrations in carcasses remained relatively stable over the first four days and raised on day 7 of decomposition under the specific conditions of this experiment, presenting a risk of causing tertiary poisoning. However, at the initial skeletal reduction stage, liver bromadiolone concentration declined, which should be considered to interpret toxicological analyses and for proper diagnosis. This experimental study provides for the first time some light to better understand the degradation of SGARs in carcasses in the wild.

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy afflicting the Cervidae family in North America, causing neurodegeneration and ultimately death. Although there are no reports of natural cross-species transmission of CWD to noncervids, infected deer carcasses pose a potential risk of CWD exposure for other animals. We placed 40 disease-free white-tailed deer (Odocoileus virginianus) carcasses and 10 gut piles in the CWD-affected area of Wisconsin (USA) from September to April in 2003 through 2005. We used photos from remotely operated cameras to characterize scavenger visitation and relative activity. To evaluate factors driving the rate of carcass removal (decomposition), we used Kaplan-Meier survival analysis and a generalized linear mixed model. We recorded 14 species of scavenging mammals (6 visiting species) and 14 species of scavenging birds (8 visiting species). Prominent scavengers included American crows (Corvus brachyrhynchos), raccoons (Procyon lotor), and Virginia opossums (Didelphis virginiana). We found no evidence that deer consumed conspecific remains, although they visited gut piles more often than carcasses relative to temporal availability in the environment. Domestic dogs, cats, and cows either scavenged or visited carcass sites, which could lead to human exposure to CWD. Deer carcasses persisted for 18 days to 101 days depending on the season and year, whereas gut piles lasted for 3 days. Habitat did not influence carcass decomposition, but mammalian and avian scavenger activity and higher temperatures were positively associated with faster removal. Infected deer carcasses or gut piles can serve as potential sources of CWD prions to a variety of scavengers. In areas where surveillance for CWD exposure is practical, management agencies should consider strategies for testing primary scavengers of deer carcass material.

Decomposition incorporates organic material delivered by Pacific salmon (Oncorhynchus spp.) into aquatic and terrestrial ecosystems of streams where salmon spawn. We hypothesized that salmon tissue decomposition would be faster, and macroinvertebrate abundance and biomass higher, in terrestrial compared to aquatic habitats, and this would be reflected in the nutritional quality of the tissue. Salmon tissue in coarse-mesh bags was placed in four habitats [terrestrial: riparian (RIP), gravel bars (GRA); aquatic: stream sediment surface (STR), buried in sediments (BUR)] in four southeast Alaska watersheds. After 2 (RIP, GRA) or 4 (STR, BUR) weeks of decomposition, tissue dry mass, macronutrient content, and macroinvertebrate colonizer abundance and biomass were determined. Overall, tissue decomposition was rapid (mean k = 0.088 day⁻¹), while nutritional quality remained high based on elemental ratios (mean C:N = 4.9; C:P = 140; N:P = 30), and differed among habitats (Linear-mixed effects model p < 0.05). Macroinvertebrate assemblages colonizing carcasses were unique to each habitat, although Diptera generally dominated. In terrestrial habitats, the dominant macroinvertebrates were Sphaeroceridae (96 % of invertebrate abundance in RIP habitat) and Calliphoridae larvae (98 % in GRA habitat). In aquatic habitats, the dominant macroinvertebrates were Chironomidae (48 % in STR habitat) and Chloroperlidae (72 % in BUR habitat). Macroinvertebrate colonizer abundance and biomass were higher in RIP (mean 286 individuals and 22 mg g⁻¹) than in other habitats (mean 4 individuals and 3 mg g⁻¹) (Friedman p < 0.05). Rapid decomposition rates and high invertebrate biomass, combined with the high nutritional quality of tissue, suggest rapid incorporation of critical salmon nutrients and energy into both aquatic and terrestrial ecosystems.