Carcass Age Research Articles

Coyotes display minimal response to Cougar scent at experimental carcass sites

Abstract Interactions among predators can have cascading impacts on communities and ecosystems. These interactions often occur around carrion, where the carrion provides a food reward, but also a risk of encountering other, potentially dominant, predators. Understanding how predators balance risk and reward at carrion, and how perceived risk changes in response to carcass origins and conditions, provides valuable insight into intraguild interactions. We investigated Coyote (Canis latrans) behavior at carrion simulated as cache sites treated with Cougar (Puma concolor) scent versus carrion used as control sites to better understand how Coyotes assess risk while feeding on carrion. Coyotes displayed similar behavior between sites treated and untreated with Cougar scent, suggesting that the presence of Cougar scent did not alter perceived risk by Coyotes in our study. Instead, Coyote behavior responded to carcass age, elevation, and whether avian scavengers had visited the carcass. Coyotes spent more time feeding, more time on camera, and touched carcasses quicker as carcass age increased. Avian scavengers appeared to compete with Coyotes, and while the presence of avian scavengers reduced time to carcass detection by Coyotes, it also decreased time spent feeding. These results suggest that carcass condition is a more important indicator of risk and reward than the presence of dominant predator scent to Coyotes. Predator scent may be an unreliable cue of immediate predator presence. Alternatively, all carcasses may be risky because dominant predators also scavenge carrion, creating similar risk regardless of previous visitation by dominant predators. These results provide insights into predator interactions and can also inform the use of scent cues in wildlife management.

Using camera traps to assess carcass use and the intraguild dynamics of understudied African mesocarnivores

The consumption of carrion is a key process in food web ecology and a common foraging strategy for facultative scavengers in the carnivore guild. As carrion represents a high-quality trophic resource, carcasses may be visited by multiple carnivore species and have the potential to act as hotspots for intraguild interactions. Mesocarnivores frequently consume carrion, yet the mechanisms used by these species to access carcasses and coexist with larger carnivores have been poorly studied. Here, we investigate the factors influencing carcass use by two understudied African mesocarnivores, the side-striped jackal (Canis adustus) and the African civet (Civettictis civetta). Using camera traps to monitor ungulate carcasses in Liwonde National Park (LNP), Malawi, we assess the influence of competing carnivores (spotted hyena; Crocuta crocuta), carcass size and carcass age on mesocarnivore detection rates. Jackals frequently consumed carrion and their detection at a carcass was positively associated with civet presence, increasing the potential for competitive interactions. Co-occurrence of jackals and civets, where both species were detected simultaneously, were mainly recorded at large (>200 kg) carcasses, suggesting competitive interactions were reduced when more abundant resources were available. Jackal and civet detection at a carcass was not influenced by the presence of spotted hyena, although we found evidence that civets use temporal partitioning to access carcasses at times of reduced spotted hyena activity. Continued monitoring of carcasses will be important to further understand carnivore coexistence dynamics, particularly as large carnivore populations recover in LNP.

Foraging risk in scavenging ecology: A study of scavenger behavior and patterns of bacterial growth

Scavenging constitutes an understudied energy pathway in terrestrial ecosystems, with important connections to disease ecology. A prevailing null hypothesis in scavenging ecology is that carcasses serve as a risk-free meal for whatever animal first encounters them on the landscape. We tested this hypothesis by focusing on a suspected risk that scavengers would face at carcasses: the risk of pathogen exposure. We conducted field trials with mouse carcasses in which we manipulated potential cues to pathogen risk and then monitored scavenger foraging decisions. Separately, we studied pathogen and commensal bacteria dynamics within mouse carcasses through time in the laboratory to better understand how carcass age might impact pathogen risk to scavengers. A visual cue to pathogen risk in the field (carcasses deployed in groups of 7 in 1 m2) caused facultative vertebrate scavengers to pass on the opportunity to feed at a rate six-times higher than for carcasses deployed singly (46.9% vs. 7.7%), suggesting an ability to perceive cues to pathogen risk at carcasses. The cues to carcass age, however, produced no effect on facultative scavenger behavior in our field trials. Laboratory trials demonstrated that both commensal enteric bacteria and a known pathogen (Listeria monocytogenes) increased at least through bloat and active decay stages in carcasses, suggesting that cues to carcass age may not help scavengers reduce pathogen risk early in decomposition. In providing evidence counter to the free meal hypothesis, our results support the continued formation of an alternative risk-based framework to understand scavenger behavior at carcasses.

Can whale-fall studies inform human forensics?

Experimental knowledge of human body decomposition in the deep ocean is very limited, partly due to the logistical challenges of deep-sea research. The literature on ecological responses to the arrival of naturally sunk and implanted whale carcasses on the seafloor represents a potential source of information relevant to questions of human body survival and recovery in the deep ocean. Whale falls trigger the formation of complex, localized, and dense biological communities that have become a point of interest for marine biologists for the past 2-3 decades. Researchers have documented whale falls by whale type, size, geographic location, water depth and water chemistry, and there have been some comparative analyses of decomposition rates and faunal presence on carcasses. We undertook a review and meta-analysis of the whale-fall literature to identify and statistically model trends relevant to human forensics. Results from studies using deep-sea cameras baited with pig carcasses and simulated carrion provided further validation of noted trends. The stages of whale carcass decomposition most relevant to human forensics are those characterised by mobile scavengers that strip the soft tissues from carcasses, and to a lesser degree, other biota that degrade skeletal material. Our statistical models used the number of faunal taxa attracted to the whale carcasses as a measure of the ecological response and the potential rate of decomposition. Negative binomial models identified significant influences of carcass age and dissolved oxygen concentration on the ecological response (taxon numbers). The strongest environmental effects were identified in data from experimental studies that implanted whale carcasses across a broad range of dissolved-oxygen conditions. We propose directions for further experimental research to refine models of environmental controls on decomposition in the deep sea. Our results also highlight the potential use of publicly available global databases on environmental conditions in the deep ocean for informing body scavenging activity and thus body survival. Applying a forensic lens to whale-fall studies provides a window into an otherwise unseen world from the standpoint of human forensic taphonomy.

Can whale-fall studies inform human forensics?

Experimental knowledge of human body decomposition in the deep ocean is very limited, partly due to the logistical challenges of deep-sea research. The literature on ecological responses to the arrival of naturally sunk and implanted whale carcasses on the seafloor represents a potential source of information relevant to questions of human body survival and recovery in the deep ocean. Whale falls trigger the formation of complex, localized, and dense biological communities that have become a point of interest for marine biologists for the past 2–3 decades. Researchers have documented whale falls by whale type, size, geographic location, water depth and water chemistry, and there have been some comparative analyses of decomposition rates and faunal presence on carcasses. We undertook a review and meta-analysis of the whale-fall literature to identify and statistically model trends relevant to human forensics. Results from studies using deep-sea cameras baited with pig carcasses and simulated carrion provided further validation of noted trends. The stages of whale carcass decomposition most relevant to human forensics are those characterised by mobile scavengers that strip the soft tissues from carcasses, and to a lesser degree, other biota that degrade skeletal material. Our statistical models used the number of faunal taxa attracted to the whale carcasses as a measure of the ecological response and the potential rate of decomposition. Negative binomial models identified significant influences of carcass age and dissolved oxygen concentration on the ecological response (taxon numbers). The strongest environmental effects were identified in data from experimental studies that implanted whale carcasses across a broad range of dissolved-oxygen conditions. We propose directions for further experimental research to refine models of environmental controls on decomposition in the deep sea. Our results also highlight the potential use of publicly available global databases on environmental conditions in the deep ocean for informing body scavenging activity and thus body survival. Applying a forensic lens to whale-fall studies provides a window into an otherwise unseen world from the standpoint of human forensic taphonomy.

Ungulate use of locally infectious zones in a re-emerging anthrax risk area.

Environmentally mediated indirect pathogen transmission is linked to host movement and foraging in areas where pathogens are maintained in the environment. In the case of anthrax, spores of the causative bacterium Bacillus anthracis are released into the environment following host death and create locally infectious zones (LIZs) around carcass sites; by grazing at LIZs, herbivores are potentially exposed to spores. Here, we used camera traps to assess how ungulate species use carcass sites in southwestern Montana and evaluated how these behaviours may promote indirect anthrax transmission, thus providing, to our knowledge, the first detailed documentation and study of the fine-scale mechanisms underlying foraging-based disease transmission in this ecosystem. We found that carcasses at LIZs significantly increased aboveground biomass of vegetation and concentrations of sodium and phosphorus, potentially making these sites more appealing to grazers. Host behavioural responses to LIZs varied depending on species, sex, season and carcass age; but, overall, our results demonstrated that carcasses or carcass sites serve as an attractant to herbivores in this system. Attraction to LIZs probably represents an increased risk of exposure to B. anthracis and, consequently, increased anthrax transmission rates. Accordingly, continued anthrax surveillance and control strategies are critical in this system.

Influence of Substrate Age on Oviposition Behavior of a Specialist Carrion Colonizer, Cochliomyia macellaria (Diptera: Calliphoridae).

The location and consumption of carrion by arthropods is a process that can be potentially distinguished temporally based on the makeup of the associated community. In fact, succession on carrion is a continuum of different generalist and specialist arthropods entering and leaving the system. Blow flies commonly associated with vertebrate remains are considered specialists due to their reliance on carrion as a source of food for offspring and protein for females. However, this specialization may come at a price; increased competition for resources and greater risk of local extinction. The present study examined the effects of the presence or absence of intraspecific colonization, carcass age, and exposure time on the colonization and oviposition responses of the specialist, primary colonizer, the secondary screw worm, Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae). Carcass age, exposure time, and colonization status significantly influenced the ovipositional response of C. macellaria. This species exhibited an oviposition preference for aged carcasses, with a tendency for higher oviposition after 8-h exposure time, but no preference between previously colonized or uncolonized carcasses. Mean egg hatch rate was also shown to be influenced by the aforementioned factors, with mean hatch rates varying between 81.26 and 90.97% across various treatments. These results provide insight into mechanisms driving succession on carrion, as well as highlight the variation observed in successional studies for the targeted species. Investigators relying on arthropod succession to indicate a time of colonization should proceed with caution in relying solely on the assumption primary colonizers only arrive and colonize fresh carrion.

Relação da precocidade de terminação e a redução da prevalência de cisticercose em bovinos

This study aimed to group cattle carcasses with similar characteristics to assess the group-specific prevalence of cysticercosis using data from the slaughter of 15,002 cattle. The following variables were recorded: carcass weight, cover fat, individual age, and prevalence of cysticercosis. A k-means clustering method was used to examine the relationship between carcass characteristics and the prevalence of cysticercosis. We did not specify the number of clusters before the analyses but used automatic methods based on a cross-validation to select the best-fitting clusters. One of the three produced clusters included carcass weight, cover fat, and age, as desired by the Brazilian meat industry. This cluster showed a reduced prevalence of cysticercosis (P = 0.0147) and earlier finishing compared with the other groups. In conclusion, earlier finishing seems to be associated with a lower prevalence of bovine cysticercosis.

Carcass age and searcher identity affect morphological assessment of sex of bats

ABSTRACTCarcasses provide an important resource for assessing the vulnerability of bat species and sexes to threats, but the reliability of sex data derived from the external morphology (sexmorph) of bat carcasses remains uncertain. We used genetic‐based assessment of sex (sexgen) to evaluate the effect of carcass age and searcher identity on sexmorph‐based assessments of eastern red (Lasiurus borealis) and hoary (Lasiurus cinereus) bat carcasses identified by 15 different searchers at a wind‐energy facility. The proportion of carcasses for which sexmorph was unknown increased from 0.11 for those recovered within a day of death, to 0.56 within 2–3 days of death, and to ≥0.82 at ≥4 days after death. The proportion of carcasses for which sexmorph was correct decreased from 0.9 for those recovered within a day of death, to 0.65 within 2–3 days of death, and to 0.25 at ≥4 days after death. The proportion of sexmorph misidentifications of the 108 fresh carcasses (collected within 24 hours of death) varied (0.0–0.43) among searchers. These results suggest that sexmorph‐based assessments should be limited to fresh carcasses. Furthermore, additional training of people who collect and identify bat carcasses from renewable‐energy facilities may improve the accuracy of sexmorph data obtained from carcasses. © 2018 The Wildlife Society.

Bird collision with power lines: estimating carcass persistence and detection associated with ground search surveys

AbstractThe quantification of bird mortality due to collision with power lines is complicated by the heterogeneity of survey methods used and the bias related to searching for carcasses on the ground (e.g., carcass persistence and imperfect detection by observers). To estimate the bias associated with ground search surveys, we conducted three 30‐d trials to test carcass persistence by placing and monitoring carcasses of red‐legged partridges (Alectoris rufa) and common pheasants (Phasianus colchicus) below power lines at 14 sites. We also conducted two detection experiments, testing the ability of 19 observers to detect bird carcasses. We used survival analysis and generalized linear mixed‐effects models to investigate the effects of site, habitat, carcass size, and survey period on both carcass persistence and detection. We also investigated the effect of carcass age on carcass persistence and the effect of the observer on carcass detection. Our findings show significant variations in carcass persistence between sites and survey periods, as well as significant interaction between these variables. The daily carcass persistence probability was highly variable between sites, with an up to eightfold variation. Carcass detection increased with increasing carcass size and was significantly affected by the microhabitat surrounding the carcass; it also varied between observers. These findings suggest that both carcass persistence and detection vary strongly and unpredictably at a small scale. As a result, conservation managers should be encouraged to conduct carcass persistence and detection experiments on sites where they aim to produce unbiased estimates of bird mortality below power lines, and these trials should be carried out in conditions similar to the mortality survey. A large‐scale, unbiased, and accurate estimate of bird collision mortality due to power lines may require substantial field effort, with a survey frequency of more than once a week.

Carcass Age and Reproductive Costs forNicrophorus orbicollis(Coleoptera: Silphidae)

The life history costs of living in microbially dense environments can be high. To assess the importance of these costs for natural selection, it is necessary to know how costs vary with environmental conditions. Adult burying beetles prepare vertebrate carcasses of varying age and states of deterioration as a resource for their young. In the present study, Nicrophorus orbicollis Say females were presented with either fresh or aged (80 h) large carcasses (30-39 g) to examine effects on their lifetime reproductive success (four reproductive attempts) and survival. Reproductive success and survival were also measured for female offspring that developed on fresh and aged carcasses. Carcass age had no measurable effect on lifetime reproductive output or life span of either parents or their adult offspring. In a separate experiment using medium-sized carcasses (22-24 g), the reproductive performance of females in a single reproductive attempt was negatively affected by carcass age (13.9% less brood mass). The results suggest that the costs of using a single older carcass are relatively minor when measured over a lifetime. Alternative costs of using older carcasses and explanations for the complex antimicrobial traits of burying beetles are discussed.

Parental care and competition with microbes in carrion beetles: a study of ecological adaptation

The investigation of the function of a complex adaptation can benefit from multiple approaches. We used comparative study and physical simulation to re-examine the hypothesis that parental adaptations enable carrion beetles (Silphidae) to better compete with carrion microbes. The comparative study used two closely related species, Nicrophorus orbicollis and Ptomascopus morio, which differ markedly in their level of care. Reproductive performance was measured using carcasses aged on field soil for 0, 3, 6 or 9 days. As expected, N. orbicollis converted more carrion biomass to offspring biomass than did P. morio (27.8% versus 16.6% on fresh carcasses) and both species produced smaller broods on aged carcasses. There was a negative interaction, however, between the level of care and carcass age on reproductive performance; the parental care advantage exhibited by N. orbicollis was less on older carcasses than on fresh carcasses, and was negligible on the oldest (6- and 9-day) carcasses. Ptomascopus morio also demonstrated superior ability to regulate the size of offspring when using carcasses of various ages. In a second experiment, we simulated antimicrobial activity of Nicrophorus anal exudates. A 6-day pretreatment with an antibacterial, an antifungal, or a combination treatment did not result in larger broods relative to those on untreated 6-day carcasses. The results call into question the hypothesis that preparation of the carcass by Nicrophorus evolved primarily as an adaptation for preventing microbial deterioration of carrion. We suggest that selection to compete with microbes may be relaxed in carrion beetles that provide elaborate parental care. A small vertebrate carcass is a potential model system for applying the comparative method to ecological function.

Estimating scavenger and search bias for collision fatality surveys of large birds on power lines in the Karoo, South Africa

Bird collision mortality associated with power lines is a global conservation challenge, but periodic carcass counts along power lines underestimate actual mortality because of survey biases. We conducted a scavenger trial over 90 days and three observer detection trials after 1, 48 and 90 days using 44 wild goose carcasses to identify explanatory variables and estimate correction factors for these biases. Scavenging activity was high but mostly occurred in situ; only 16% (95% binomial CI 5–27%) of carcasses were removed by the end of the 90-day trial period (all within the first three weeks). Observer experience did not significantly affect detection rate, with experienced observers locating 75% (95% CI 68–83%) of carcasses compared with 67% (95% CI 58–75%) by naïve observers. Vegetation height, distance from the line and carcass spread were significant explanatory variables. The pattern in detection rate linked to carcass age was variable; there were fewer detections after 48 days, but rates at day 1 and day 90 were similar for experienced observers because bleached bones were highly visible. This suggests that long survey intervals are acceptable for the detection of large bird carcasses in arid environments such as the Karoo where collisions are infrequent but widespread events.

Blow fly responses to semiochemicals produced by decaying carcasses

Volatiles from mouse carcasses in decay stages ranging from fresh to 33 days old were used to investigate oriented flight and landings in male and female blow flies of Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). Oriented flight increased significantly from 36% towards fresh carcasses to 68%, 61% and 65% towards carcasses aged 3 days, 6 days and 9 days, respectively. Carcasses aged 20 days and 33 days were significantly less attractive, achieving 51% and 41% attraction, respectively. No differences emerged between the sexes in oriented flight, but a significant increase in female landings at the most attractive carcasses was observed. Headspace collections from the different stages of decay showed a succession in the volatile profile emitted from the carcasses and identified nine chemicals which peak in quantity in concurrence with the most attractive stages of decay. Three of these chemicals also showed dose-response effects as indicated by a significant correlation between the amount present and the proportion of flies responding. Blow flies are important pests and efficient traps are needed. The significant interaction between fly sex and carcass age highlights behavioural differences between male and female blow flies which can be exploited in blow fly trapping. Three new volatile chemicals, butylated hydroxyl toluene, 3-hydroxy-2-butanone and nonanal, emitted from dead mice are suggested as potential attractants.

Effects of paratuberculosis on Friesian cattle carcass weight and age at culling

Bovine paratuberculosis (PTB) causes major economic losses to dairy farmers because of decreased milk production, poor body condition, weight loss and early culling. The aim of this study was to evaluate the effect of Mycobacterium avium subspecies paratuberculosis (MAP) infection on carcass weight and age at slaughter in Friesian cattle. A total of 1,014 adult cows slaughtered at two local abattoirs in the Basque Country were included in this study. MAP infection was determined by different methods: indirect ELISA on blood samples, detection of MAP in tissues by culture and real time PCR (rtPCR), and histopathological examination. Serial and parallel interpretations of these methods were also considered for setting the upper and lower infection rates. MAP infection was confirmed by at least one test in 58.9% of animals. Most infected cows were detected by histopathology (46.9%) and rtPCR (29.6%). Overall estimates of carcass mean weight losses ranged from 3.7% for cases identified by the presence of microscopic specific PTB inflammatory lesions to 12.4% for cases with positive results in the paratuberculosis antibody ELISA test. Isolation of high bacterial loads in tissues and occurrence of diffuse granulomatous enteritis were associated with the highest weight loses, 22.2% and 26.0% respectively. The life expectancy of seropositive cows and those showing diffuse lesions was reduced by nearly one year compared to that of non-infected ones. Our results provide consistent evidences of PTB effect on the reduction of slaughter weight and lifespan of dairy cows, which could be considered as surrogates of clinical disease.

Evaluation of Station Testing of Pigs

Carcass measurements, growth rate and age at slaughter were studied for the Landrace, Yorkshire and Hampshire breeds, using 4117, 2224, 561 test groups respectively, each group consisting of two pigs, representing 1091, 593 and 117 sires. Heritabilities for lean percentage were; 0.70, 0.81 and 0.27; for percent meat ± bone in back; 0.64, 0.73 and 0.25; for percent meat ± bone in ham; 0.73, 0.87 and 0.51; and for ham percentage 0.43, 0.43 and 0.28 for Landrace, Yorkshire and Hampshire respectively. Lean percentage had positive genetic correlations with daily gain, meat colour (unfavourable), and dressing percentage. Carcass length had very low genetic correlations with lean percentage. Dressing percentage had positive genetic correlations with meat colour (unfavourable), percent meat ± bone in back and ham and lean percentage for both Landrace and Yorkshire. Possible ways of improving the utilization of the results of carcass evaluation are discussed.

GROWTH AND CARCASS TRAITS OF CATTALO, HEREFORD, AND 1/4-BRAHMAN BULL CALVES

The 1/4-Brahman bull calves exceeded those of the cattalo and Hereford by 19.6 and 14.8% in weaning weight. However, the Hereford surpassed the 1/4-Brahman and the cattalo by 11.1 and 14.9% in feedlot average daily gain. Cattalo (cattle × bison species cross) bulls weighed 17.7 and 12.0% less than 1/4-Brahman and Hereford bulls just before slaughter at an average age of 425 days. Similar differences were apparent for cold carcass weight. When age-of-dam and age-at-slaughter were covariate factors, area of the longissimus dorsi from 1/4-Brahman calves was larger by 13.5 and 8.7% than those from cattalo and Hereford. Fat thickness over the 1. dorsi did not differ among groups. Carcass weight and age at slaughter were covariates for the weights of meat cuts. Weights of loin, round, or plate cuts did not differ among groups. However, the rib cut from the 1/4-Brahman was lighter than that from the cattalo and Hereford, and the chuck cut was heavier. The Hereford exceeded the 1/4-Brahman in total weight of the more expensive rib–loin–round cuts. Warner-Bratzler shear estimates of tenderness did not differ among groups. Average fat thickness over the 1. dorsi was not significantly correlated to any of the means of the shear test on raw or broiled samples. In general, 1/4-Brahman and Hereford groups each exhibited superiority over the other two groups for several traits, while cattalo bulls did not exceed the other two groups in any of the traits considered in this study.

Factors associated with differences in carcass conformation in lamb

Abstract Factors associated with differences in carcass conformation were studied in three experiments involving 85 pairs of lambs, half of which had been selected as having blocky conformation and half leggy conformation. Pairs of carcasses were matched for carcass weight and age at slaughter. The blocky carcasses contained more fat and less red meat and bone than the leggy carcasses. They also had a higher proportion of the fatter cuts (loin, ribs, and flap) and a lower proportion of the leaner cuts such as the leg. A taste panel found the palatability characteristics of leg meat from both types of carcasses acceptable and did not differentiate between them. The differences in conformation strongly influenced the export grading of the carcasses, the blocky carcasses grading predominantly Prime Down Cross and the leggy carcasses mainly Prime Crossbred and Y. Southdown sires produced the blockiest carcasses and the other breeds studied produced the leggiest carcasses. Within-breed variation was also noted...