The discrepancy between fire ant recruitment to and performance on rodent carrion

Ants have not been considered important in the process of vertebrate carrion decomposition, but a recent literature review reported over 150 carrion-visiting ant species. Though many ant species have been observed to remove carrion tissue and consume carrion-exuded liquids, the significance of ant recruitment to vertebrate carrion is poorly understood. We conducted a combination of field and laboratory experiments to quantify red imported fire ant recruitment to rodent carrion and determine whether consuming rodent carrion is beneficial to ant colony performance. In the field, 100% of rat carcasses were rapidly colonized by fire ants at high abundances. In our laboratory experiment, the performance of mice-fed fire ant colonies was poor when compared to colonies that were fed mice and insects or insects only. Our results suggest that there is a discrepancy between high levels of fire ant recruitment to vertebrate carrion and the poor colony performance when fed carrion. We hypothesize that fire ants are attracted to vertebrate carrion not because it is a high-quality food, but rather because it hosts large numbers of other invertebrates that can serve as prey for fire ants, potentially showcasing an interesting case of tritrophic interaction in carrion ecology.

Relative Roles of Blow Flies (Diptera: Calliphoridae) and Invasive Fire Ants (Hymenoptera: Formicidae: Solenopsis spp.) in Carrion Decomposition

Fire ants (Solenopsis spp.) have increasingly been reported from carrion in the southeastern United States and are now a part of the normal succession community. There have been previous observations of these ants altering carrion and preying on other carrion-attendant fauna; however, the overall effects of these activities on carrion decomposition rates, community composition, and blow fly larval development are poorly understood. Alteration of these ecological processes by fire ants could affect the forensic interpretation of entomological data. We conducted a study in Mississippi and Florida whereby portions of the succession fauna were excluded from access to pig carrion to study the relative effects of fire ants and blow flies on carrion decomposition and succession: a control with all fauna having access, a second treatment where fire ants and other geophilic taxa were excluded, and a third treatment in which blow flies and other large organisms were excluded. Fire ants inflicted lesions in the carrion, buried portions that touched the ground, and preyed on some members of the succession fauna. Their exclusion did not affect carrion decomposition rates that were measured but slightly affected the overall carrion community, and strongly affected the oviposition and development of blow flies. Despite the presence of fire ants early in the control, blow flies were eventually able to overcome predation of eggs and larvae, continue colonization, and complete development; however, the delay in the colonization of blow flies on carrion could affect the determination of postmortem intervals when development rates of blow flies are considered in the calculation.

Forensic Entomology: Arthropods collected on decomposing pig carrions in Warri, Delta State, Nigeria.

A data base of arthropods of forensic importance was collected from pig carrions from 10th June to 10th August 2017 in the Warri city, 3 pigs were killed by cervical dislocation and left to decay while the daily assemblage of arthropods were collected from it. The result showed 5 stages of the carrion decomposition; fresh, bloated, active decay, advance decay and dry decay correspondingly despite that there was only a single sequence of decomposition. Entomofauna groups from 3 orders of Diptera, Coleoptera and Hymenoptera, with ten families were collected during the study while 233 insects were collected at the fresh stage, 324 were collected at the bloat stage, and 328 were recorded at the active decay stage, 405 at the advance decay stage and only 158 at the dry decay stage. The dominance index was high (0.09) at the dry decay stage but low (0.06) at the bloat, active decay and advanced decay stages. Shannon–Wiener index (H) was high (2.91) in the advanced decay stage but was low (2.52) at the dry decay stage. Arthropod from the orders of Diptera and Coleoptera were forensically significant as they used the carcasses for feeding and oviposition and could be used in the estimation of the post mortem interval while the order Hymenoptera used the carrion as extension of their habitat and as predatory ground to the necrophagous groups, it is advocated that more studies be carried out in different seasons using different animal models to create dependable data base of forensically importance arthropods in Warri and its environs.

Insect reproductive behaviors are important mediators of carrion nutrient release into soil

Current declines in terrestrial insect biomass and abundance have raised global concern for the fate of insects and the ecosystem services they provide. However, the ecological and economic contributions of many insects have yet to be quantified. Carrion-specializing invertebrates are important mediators of carrion decomposition; however, the role of their reproductive activities in facilitating this nutrient pulse into ecosystems is poorly understood. Here, we investigate whether insects that sequester carrion belowground for reproduction alter soil biotic and abiotic properties in North American temperate forests. We conducted a field experiment that measured soil conditions in control, surface carrion alone, and beetle-utilized carrion treatments. Our data demonstrate that Nicrophorus beetle reproduction and development results in changes in soil characteristics which are consistent with those observed in surface carrion decomposition alone. Carrion addition treatments increase soil labile C, DON and DOC, while soil pH and microbial C:N ratios decrease. This study demonstrates that the decomposition of carrion drives soil changes but suggests that the behaviors of insect scavengers play an important role in the release of carrion nutrients directly into the soil by sequestering carrion resources in the ecosystem where they were deposited.

Olfactory Choice for Decomposition Stage in the Burying Beetle Nicrophorus vespilloides: Preference or Aversion?

Sensory cues predicting resource quality are drivers of key animal behaviors such as preference or aversion. Despite the abundance of behavioral choice studies across the animal kingdom, relatively few studies have tested whether these decisions are driven by preference for one choice or aversion to another. In the burying beetle Nicrophorus vespilloides, adult pairs exhibit parental care to raise their offspring on a small carrion resource. We tested whether carrion decomposition stage affected brood quantity and quality and found that mating pairs had significantly more offspring on fresher carcasses. To determine whether this observed reproductive benefit correlates with maternal preference behavior, we conducted a series of olfactory trials testing mated female preferences for mouse carcasses of differing decomposition stages. When given the option between fresh and older carcasses, females associated significantly more with fresher, 1-day old carcasses. However, this behavior may be driven by aversion, as females that were given a choice between the 7-day old carcass and a blank control spent significantly more time in the control chamber. We characterized volatile organic compound profiles of both carcass types, highlighting unique compounds that may serve as public information (sensu lato) conveying resource quality information to gravid beetles.

Local and Landscape Effects on Carrion-Associated Rove Beetle (Coleoptera: Staphylinidae) Communities in German Forests

Intensification of anthropogenic land use is a major threat to biodiversity and thus to essential ecosystem services provided by insects. Rove beetles (Coleoptera: Staphylinidae), which react sensitively to habitat changes, are species-rich colonizers of vertebrate cadavers and contribute to the important ecosystem service of carrion decomposition. The unveiling of anthropogenic and environmental drivers that modify carrion-associated rove beetle communities should improve our understanding of the plasticity of cadaver decay. We report the presence of 80 rove beetle species on 65 decomposing piglet cadavers at forest sites characterized by a gradient of management intensity across three geographic regions in Germany. Local and landscape drivers were revealed that shape beetle abundance, diversity, and community composition. Forest management and regions affect rove beetle abundance, whereas diversity is influenced by local habitat parameters (soil pH, litter cover) and regions. The community composition of rove beetles changes with management intensification by promoting generalist species. Regarding single species, Philonthus decorus and Anotylus mutator are linked to unmanaged forests and Ontholestes tessellatus to highly used forest stands. The spatial information provided about carrion-associated rove beetle communities in German forests is not only of carrion-ecological but also of forensic entomological interest.