- Knoxville, TN, United States
- Anthropology, Entomology, Forensic Anthropology, Death and Burial (Archaeology), Vulture, Geographic Information Systems (GIS), and 16 moreGeo-spatial analysis with GIS and GPS, Taphonomy, Animal Scavenging, Satellite Telemetry, Oil and gas, Skeletal trauma, Outdoor Pigs, Decomposition, Black vulture, Raptor Biology, Birds of prey, Ornithology, Avian Ecology, Forensic Taphonomy, Turkey Vulture, and Vulturesedit
Vultures are catalysts of the decomposition process, but their scavenging is under reported in the academic literature. Moreover, forensic scientists have realized that vultures will feed on human decedents in addition to road-kill,... more
Vultures are catalysts of the decomposition process, but their scavenging is under reported in the academic literature. Moreover, forensic scientists have realized that vultures will feed on human decedents in addition to road-kill, thereby complicating forensic time since death estimations. Research from Texas State University's Forensic Anthropology Research Facility (FARF) proves in contrast to common beliefs that vultures arrive early during the decomposition process and leave few clues to indicate their prior scavenging presence. As a result, one option to aid law-enforcement during medicolegal investigations involving unidentified human remains will be to identify vultures' preferred and most likely scavenging environments. The goal of this research was to use Global Positioning System (GPS) based satellite telemetry to track vultures that were trapped, tagged, and released from FARF to test a new methodology that involved using flight altitude to identify possible vulture scavenging locations. The hourly movements of four black vultures (Coragyps atratus) and two turkey vultures (Cathartes aura) were monitored for six months during this baseline study. Geospatial analyses were conducted within a Geographic Information System (GIS), with a second research goal being to solely use open access geographic datasets for the Texas study area. During this presentation, attendees will learn about the challenges faced when using satellite telemetry to study wildlife along with the wealth of data and knew knowledge one can gain about vulture behavior.
Research Interests:
Avian and terrestrial scavengers play a critical role in both forensic anthropology and archaeological investigations by (1) accelerating decomposition through rapid tissue removal, (2) causing pseudo perimortem trauma on the bones, and... more
Avian and terrestrial scavengers play a critical role in both forensic anthropology and archaeological investigations by (1) accelerating decomposition through rapid tissue removal, (2) causing pseudo perimortem trauma on the bones, and (3) dispersing the remains from the original deposition site. Previous studies have noted that vultures accelerate decay and much attention has been given to the impacts terrestrial scavengers have on physical anthropology investigations. However, few studies have assessed differentiating and quantifying avian and terrestrial scavenging evidence occurring on the same set of skeletal remains. To address the challenges in distinguishing avian from terrestrial skeletal trauma, we placed 43 deceased pigs in the fresh stage of decay across 6,000 km 2 in south central Texas during 2011 and 2012. The pigs were not protected from either avian or terrestrial scavengers and each scavenging sequence was monitored via remote infrared photography. Results revealed that turkey vultures (Cathartes aura) and black vultures (Coragyps atratus) were the most frequent scavenger (N=38) at the 43 pig trials and the gray fox (N=8) (Urocyon cinereoargenteus) was the most frequent terrestrial scavenger. However, the crested caracara (Caracara cheriway) had the greatest impact on the presence or absence of skeletal remains because this bird did not consume the remains but instead would grab a bone and then fly away. Knowledge of the caracara's tendency to steal bones from a site both during and after scavenging episodes of vultures and other terrestrial scavengers can offer knew insight as to why expected skeletal data is absent from deposition sites.
Research Interests:
After attending this presentation, attendees will be aware of misconceptions regarding when and how scavengers locate carrion. This presentation will impact the forensic community by illustrating that forensically important animal... more
After attending this presentation, attendees will be aware of misconceptions regarding when and how scavengers locate carrion. This presentation will impact the forensic community by illustrating that forensically important animal scavengers appear early in the postmortem interval regardless of whether the food is actually decomposing or simply looks to be decomposing. Acceleration of decay by animal scavengers has been attributed to turkey vultures, which use smell to locate decay, and black vultures, which rely on sight. Once vultures hone in on a carrion source, they land and rapidly remove soft tissues from the body. Once skeletonization has been reached, terrestrial scavengers will then scatter and damage the bones. Although researchers are aware that turkey vultures can locate food through smell, the ability of black vultures to use the sense of smell to locate food is debatable. New knowledge on vultures' ability to locate food via visual versus olfactory indicators will contribute to the understanding of both vulture scavenging behavior and the postmortem roles vultures have in forensic contexts involving buried or concealed remains. To test the role of sight versus olfaction in vultures' ability to detect carrion, a taxidermied juvenile pig was placed seven times at three different site types where vultures had previously scavenged real juvenile pigs in the fresh stage of decay. The three site types included the Texas State Forensic Anthropology Research Facility (FARF), a cattle pasture located over 1 km from FARF, and rotating pig placement sites that changed locations with each trial. The Rotate Sites were located at least 7 km from the other two site types. On September 9, 2012, the project began by placing a juvenile pig in the fresh stage of decay at each of the three site types. This process was repeated every two weeks eight more times to determine if the site type affects vulture scavenging. Three real pigs were placed at the three sites during each of Trials 1-4. After the fourth placement of the decaying pigs, vultures had scavenged 11 of the 12. Beginning on November 4, 2012 (Trial 5), both real pigs and the taxidermied pig were placed, and the taxidermied pig was placed at sites where the real pigs had been scavenged by vultures. As more real pigs were placed and scavenged by vultures, additional sites to place the taxidermied pig became available. During Trials 5-9, the taxidermied pig was placed biweekly at five of the Rotate Sites that had involved vulture scavenging of the real pigs. Following the conclusion of the ninth trial, the taxidermied pig was placed a sixth and seventh time at the cattle pasture and FARF sites respectively. All pigs were monitored with a motion activated game camera. Results reveal that animal scavengers arrive early in the postmortem interval regardless of whether the food source is dead or appears to be dead. Scavengers at the taxidermied pig included turkey vultures, a red tailed hawk, a crow, coyotes, dogs, foxes, opossums, raccoons, and a bobcat. Other animal visitors included deer, cows, and rabbits. Surprisingly absent was the black vulture, a scavenger said to rely on sight. This is surprising because 121 black vultures were present at the real carrion placed during the nine trials. In addition to advancing the discussion on how scavengers detect a carrion source, this research contributes to the discussion of trauma scavengers inflict. During this study, scavengers removed an ear and the tail of the taxidermied pig and left linear scratch marks on the abdomen. This trauma is consistent with scavengers going for easily removable and accessible parts of the body as seen on real carrion. The unexpected presence of forensically important scavengers at the taxidermied pig, a pig unable to decompose and unaffected by accumulated degrees, will promote a discussion on the need to include avian and terrestrial scavengers in future taphonomic studies.
Research Interests:
After attending this presentation, attendees will have a better understanding of the benefits and limitations of using satellite telemetry and Geographic Information Systems (GIS) in forensic contexts and taphonomic research. Satellite... more
After attending this presentation, attendees will have a better understanding of the benefits and limitations of using satellite telemetry and Geographic Information Systems (GIS) in forensic contexts and taphonomic research. Satellite telemetry, or the remote Global Positioning System (GPS) satellite tracking of wildlife, provides location and altitude data on animal movements such as vulture flight patterns. This presentation will impact the forensic community by providing new insight concerning (1) whether or not vultures can be trained and then tracked as a way to locate human remains, and (2) the methodological limitations of satellite telemetry when applied to studies involving terrestrial scavengers. The circling vulture is a universal symbol of death, and these obligate scavengers use olfaction to search for fresh decay. In previous instances where individuals were reported missing, anecdotal accounts have suggested that investigators should search the area where circling vultures were seen. However, the circling vulture may be soaring within a wind vortex, or thermal, rather than about to scavenge a set of decaying remains. To learn if vulture flight patterns can be used to identify vulture-scavenging locations, six vultures were trapped, GPS tagged, and then released from the Texas State Forensic Anthropology Research Facility (FARF) in San Marcos, Texas. The hourly locations of the vultures were monitored for six-months and resulted in over 15,000 GPS data points that included information on geographic location (distance), altitude, and flight speed. These variables were analyzed using GIS, allowing for the identification of scavenging behaviors in vultures. Providing the ability to detect likely vulture scavenging locations from GPS tracking, satellite telemetry provides a wealth of information useful for advancing forensic taphonomy research. Nevertheless, limitations of satellite telemetry should be considered before a tracking study begins. These limitations include costs and logistical difficulties with trapping and tagging animals as seen in the examples below. In 2014, a medical examiner (ME) consulted with this research regarding his plan to trap, train, and then release and track a GPS-equipped vulture to locate human decedents. Because vultures travel long distances, the idea of training a vulture to locate a human body in a fixed, small area is not realistic. For example, turkey vultures released from FARF traveled throughout Texas and into Oklahoma. Moreover, rather than a specific human or animal food source, vultures prefer to locate and scavenge fresh carrion by using their sense of smell. The benefits of the ME's proposal did not outweigh the costs in terms of time or finances. Forensic anthropologists have suggested that the vulture tracking project be repeated using terrestrial scavengers such as coyotes. Based on experience, this could provide new insight concerning the distance a coyote could potentially travel with a bone from a forensic case. However, detecting the scavenging behavior of a coyote within the GPS data is a concern. For each vulture tracking location, GPS transmitters provided altitude and flight speed. Hourly changes in these two values allowed for the detection of possible scavenging locations. A coyote, however, is always close to the ground, which makes it difficult to determine if a coyote is resting or scavenging. Therefore, the information that was most helpful in identifying the patterns in vulture behavior will be absent in terrestrial scavengers. Thus, satellite telemetry will not work as well for land scavengers because of the difficulty in identifying their scavenging behaviors. Despite the limitations associated with GPS tracking research, with careful planning a GPS study can provide new insight into scavenging behavior and substantially benefit the forensic community in solving cases for years to come. The use of migratory birds and other animals for research was conducted with federal, state, and university approval. All vultures were released unharmed, and permits are available upon request.
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After attending this presentation attendees will be aware of how sites with repetitive carrion placement, such as an outdoor forensic facility, affect animal scavenging rates and behavior. Attendees will also become aware of the... more
After attending this presentation attendees will be aware of how sites with repetitive carrion placement, such as an outdoor forensic facility, affect animal scavenging rates and behavior. Attendees will also become aware of the applicability of temporal scavenging data collected at the Texas State Forensic Anthropology Research Facility (FARF) to forensic contexts that lack the continuous carrion presence found at FARF.
This presentation will impact the forensic community by addressing the possibility of learned behavior and accelerated arrival times in avian scavengers at FARF as a result of repetitive decomposition studies occurring at this site.
In recent years, forensic anthropology research facilities have gained much attention because they offer a means of conducting decomposition research that aims to benefit law enforcement. These outdoor decomposition facilities provide invaluable skeletal data with associated demographics, but no researchers have investigated the impact these facilities may be having on vertebrate scavenging behavior. This study focuses on vulture scavenging behavior and addresses the possible variability in vulture scavenging rates at FARF as a consequence of repetitive decomposition studies occurring at this site.
To address the possibility of learned behavior in vultures scavenging at FARF, a series of 14 decomposition trials were conducted at three site types over a two-year period to test the hypothesis that type of scavenging site affects the amount of time between carrion exposure and the initiation of a vulture scavenging event. Each trial involved placing a single juvenile pig at each of the three site types, which included the following: (1) FARF – repetitive carrion placement in a single location; (2) Rotate Sites – repetitive carrion placement at different locations; and, (3) Stationary Site – repetitive carrion placement in a single location. The FARF and Stationary sites were over 1km apart and the Rotate Sites were distributed across an area of 6,000 km2 spanning from Austin to San Antonio. The three pigs used in each trial were placed in uncaged locations on a single day. All sites were equipped with a motion activated infrared wild life camera and a weather station programmed to record climatic variables using one-minute sampling intervals. The cameras and the weather stations were in operation 24-hours a day throughout the duration of the study.
Temporal data were calculated for minutes between researcher departure from the site until the time of vulture arrival at the carrion. Departure time was chosen based on the assumption that vultures would not arrive while a human was at the site. In addition, accumulated degree minutes (ADM) were calculated for the time between pig placement and vulture arrival to account for the assumption that vulture arrival at carrion is based on their detection of temperature dependent volatiles being omitted during different stages of decomposition. To account for some of the pigs being placed in the evening after vultures had returned to their roosts, a second ADM value was calculated for temperatures only recorded during the day. Solar radiation values of 0.6 W/m2 (i.e., nighttime) were used to distinguish daytime and nighttime temperature values.
One-way ANOVAs testing for differences between the type of scavenging site and time of vulture arrival were performed on the three temporal values described above and reveal an absence of statistical differences between site type and vulture arrival times. Results also indicate that scavenging rates obtained through FARF research are applicable to scavenging rates occurring outside of FARF within the 6,000 km2 geographical range used in this study so long as the carrion size, type, and stage of decomposition are the same between FARF and the location in question. Furthermore, the similarity between scavenging rates at FARF and other sites were based on carrion placement occurring two weeks apart, which suggests this may be a best practices temporal benchmark for future scavenging studies. Lastly, this study reveals that although variation exists in vulture scavenging rates, the repetition of carrion using two-week intervals at a particular site does not accelerate or cause differences in vultures’ arrival time at recently exposed carrion.
This presentation will impact the forensic community by addressing the possibility of learned behavior and accelerated arrival times in avian scavengers at FARF as a result of repetitive decomposition studies occurring at this site.
In recent years, forensic anthropology research facilities have gained much attention because they offer a means of conducting decomposition research that aims to benefit law enforcement. These outdoor decomposition facilities provide invaluable skeletal data with associated demographics, but no researchers have investigated the impact these facilities may be having on vertebrate scavenging behavior. This study focuses on vulture scavenging behavior and addresses the possible variability in vulture scavenging rates at FARF as a consequence of repetitive decomposition studies occurring at this site.
To address the possibility of learned behavior in vultures scavenging at FARF, a series of 14 decomposition trials were conducted at three site types over a two-year period to test the hypothesis that type of scavenging site affects the amount of time between carrion exposure and the initiation of a vulture scavenging event. Each trial involved placing a single juvenile pig at each of the three site types, which included the following: (1) FARF – repetitive carrion placement in a single location; (2) Rotate Sites – repetitive carrion placement at different locations; and, (3) Stationary Site – repetitive carrion placement in a single location. The FARF and Stationary sites were over 1km apart and the Rotate Sites were distributed across an area of 6,000 km2 spanning from Austin to San Antonio. The three pigs used in each trial were placed in uncaged locations on a single day. All sites were equipped with a motion activated infrared wild life camera and a weather station programmed to record climatic variables using one-minute sampling intervals. The cameras and the weather stations were in operation 24-hours a day throughout the duration of the study.
Temporal data were calculated for minutes between researcher departure from the site until the time of vulture arrival at the carrion. Departure time was chosen based on the assumption that vultures would not arrive while a human was at the site. In addition, accumulated degree minutes (ADM) were calculated for the time between pig placement and vulture arrival to account for the assumption that vulture arrival at carrion is based on their detection of temperature dependent volatiles being omitted during different stages of decomposition. To account for some of the pigs being placed in the evening after vultures had returned to their roosts, a second ADM value was calculated for temperatures only recorded during the day. Solar radiation values of 0.6 W/m2 (i.e., nighttime) were used to distinguish daytime and nighttime temperature values.
One-way ANOVAs testing for differences between the type of scavenging site and time of vulture arrival were performed on the three temporal values described above and reveal an absence of statistical differences between site type and vulture arrival times. Results also indicate that scavenging rates obtained through FARF research are applicable to scavenging rates occurring outside of FARF within the 6,000 km2 geographical range used in this study so long as the carrion size, type, and stage of decomposition are the same between FARF and the location in question. Furthermore, the similarity between scavenging rates at FARF and other sites were based on carrion placement occurring two weeks apart, which suggests this may be a best practices temporal benchmark for future scavenging studies. Lastly, this study reveals that although variation exists in vulture scavenging rates, the repetition of carrion using two-week intervals at a particular site does not accelerate or cause differences in vultures’ arrival time at recently exposed carrion.
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Avian and terrestrial scavengers play a critical role in both forensic anthropology and archaeological investigations by (1) accelerating decomposition through rapid tissue removal, (2) causing pseudo perimortem trauma on the bones, and... more
Avian and terrestrial scavengers play a critical role in both forensic anthropology and archaeological investigations by (1) accelerating decomposition through rapid tissue removal, (2) causing pseudo perimortem trauma on the bones, and (3) dispersing the remains from the original deposition site. Previous studies have noted that vultures accelerate decay and much attention has been given to the impacts terrestrial scavengers have on physical anthropology investigations. However, few studies have assessed differentiating and quantifying avian and terrestrial scavenging evidence occurring on the same set of skeletal remains. To address the challenges in distinguishing avian from terrestrial skeletal trauma, we placed 43 deceased pigs in the fresh stage of decay across 6,000 km 2 in south central Texas during 2011 and 2012. The pigs were not protected from either avian or terrestrial scavengers and each scavenging sequence was monitored via remote infrared photography. Results revealed that turkey vultures (Cathartes aura) and black vultures (Coragyps atratus) were the most frequent scavenger (N=38) at the 43 pig trials and the gray fox (N=8) (Urocyon cinereoargenteus) was the most frequent terrestrial scavenger. However, the crested caracara (Caracara cheriway) had the greatest impact on the presence or absence of skeletal remains because this bird did not consume the remains but instead would grab a bone and then fly away. Knowledge of the caracara's tendency to steal bones from a site both during and after scavenging episodes of vultures and other terrestrial scavengers can offer knew insight as to why expected skeletal data is absent from deposition sites.