A study was conducted to examine the timing and nature of decay and disarticulation in small vertebrates, using an experimental regime that allowed comparison among different environments, and different size classes of amphibians, reptiles, birds, and mammals. Decay and disarticulation of freshly killed small vertebrates was documented in freshwater and seawater aquaria as well as outdoor terrestrial settings protected from scavengers by partially buried cages. Experimental animals included salamanders (two sizes), lizards, finches, doves, mice, rats, squirrels, and rabbits. The study area was hot and dry (southern California), with scattered winter rains. Some specimens of each species in the terrestrial environment were transferred after about one month to one of two other environments - freshwater, or an outdoor terrestrial cage simulating increased rainfall. In water the carcasses' flesh decayed by bacterial action in one to six months, but insect larvae removed the flesh from terrestrial carcasses within two weeks, leaving dry, desiccated carcasses that changed little over a four to 11 month period. The process of decay and disarticulation was greatly affected by differences in properties of the skin between species and the reaction of each type of skin to drying or water saturation. Disarticulation time was shortest in water, followed by the high rainfall treatment, then dry terrestrial environment. The sequence of disarticulation varied considerably, especially in the terrestrial treatment, but heads and limbs tended to separate from the body first, and then individual bones separated from the limbs. Also, the pattern of tooth loss or cracking differed among environments. These data provide an actualistic analogue to assist in the interpretation of some parameters of fossil assemblages, including maximum time between death and burial of partially or fully articulated small vertebrate fossils (about 3 months in water, but over a year in dry terrestrial conditions), or the likely paleoenvironment in which an assemblage accumulated.
The decomposition of two ostrich (Struthio camelus) chicks (body masses 2.1 kg and 11.5 kg) was observed in a terrestrial and an aquatic setting, respectively, in a hot and arid climate with temperatures ranging from 25-40°C. Special attention was given to the observation of the release of gastroliths from the body cavity. The results show that the gastroliths can be set free from carcasses with a body weight <12 kg after relatively short periods (3-6 days), and that a separation in an aquatic environment is likely because of prolonged floating of the carcass.
Experiments with lamb carcasses were used to investigate whether any identifiable "damage signatures" are imparted by wooden spears on bones and whether these differ between a javelin and a thrusting spear. The data from the experiments demonstrated no distinction in damage caused by the two types of spears. Both spears caused high frequencies of saw-toothed fractures on ribs and vertebrae and the javelin inflicted a spiral fracture on a humerus. However, the most conclusive evidence of projectile usage was in the form of puncture wounds on scapulae. Some of the experimental damage recorded is similar to that caused by other taphonomic processes. These experiments illustrate the effectiveness and durability of wooden spears as potential hunting implements and provide insight regarding the tools, technology and subsistence strategies of Middle and Late Pleistocene hominids.
We argue that the evolutionary significance of prehistoric hominid carnivory will be better appreciated if taphonomic tests for evaluating the initial encroachment on the larger carnivoran paleoguild by Oldowan hominids are developed and applied to zooarchaeological assemblages. We propose that the development of taphonomic tests should be guided by three premises: 1) taphonomic measures used to test scenarios of hominid carnivory should be free of interpretive equifinalities; where equifinalities are currently suspected, these must be identified and broken; 2) carnivorans are not a single, homogeneous, taphonomic agent; actualistic research is needed to differentiate the preservable feeding traces of individual carnivore taxa; 3) multiple carnivore species should be assumed to have been involved in creation and modification of bone assemblages; the recognition of the timing and nature of the access of each carnivore to prey carcasses should be sought.
We offer some fundamental steps in developing a methodology to satisfy this research agenda, integrating information from naturalistic observations of carnivoran feeding on mammalian prey carcasses, actualistic studies that simulate the timing of hominid access to these prey carcasses, and functional aspects of presumed carnivoran paleoguilds defined by carcass size-specific edible tissue specialization and bone modification capabilities. We focus on skeletal element and element portion profiles in conjunction with the incidence, anatomical distribution and morphology of tooth marking as the relevant taphonomic measures. The ultimate goal is to diagnose and zooarchaeologically identify unambiguous traces of individual carnivoran taxa and ecological scenarios involving feeding sequences by multiple carnivore taxa, including hominids.
A Deposition Mechanism for Holocene Miring Bone Deposits, South Island, New Zealand.
Jamie R. Wood, Trevor H. Worthy, Nicolas J. Rawlence, Susan M. Jones, Stephen E. Read.
Keywords: BONE, DEPOSITION, GIS, HOLOCENE, MIRING, MOA, NEW ZEALAND, WETLAND
[+info] VOLUME 6. ISSUE 1. 2008 (1 issue)
Localised deposits of Late Pleistocene and Holocene bird bones occur in wetlands throughout New Zealand. These are characterised by dense accumulations of mostly disarticulated bones, with assemblages dominated by large, flightless bird taxa; in particular the extinct ratite moa (Aves: Dinornithiformes). A wide range of deposition mechanisms were historically proposed for these sites, including large floods and stampedes during wildfires. We outline a simple method for analysing the orientation and spatial distribution of bones within these deposits using GIS software, and apply this method to the interpretation of three such deposits from South Island, New Zealand. The results are consistent with non-catastrophic, periodic miring of individual moa. Long bones within these sites were preferentially orientated and subhorizontally inclined, indicating post-deposition disarticulation and movement of the bones within the sediment by sediment liquefaction and raking from the legs of mired birds, with a possible influence from water flow. Small, light skeletal elements were significantly under represented in the deposits. This may be due to post-mortem scavenging or weathering of vertebra and crania, 'pumping' to the surface of light, buoyant elements during liquefaction events, or crushing of these elements by subsequently mired birds.
We explored decay rate dynamics in the early decomposition process of Gallus gallus. Our initial hypothesis was that the variation of the mass decay rate is sensitive to the alterations experienced by the carcass during decomposition. In order to establish a framework for the different patterns of carcass alteration, a sample with successive ontogenetic stages (from embryo to adult), set in three environmental conditions (subaerial, burial, and water-submerged), was examined over an 18-day experimental period. Values of the average mass loss and decay rate, and a measure of the overall decomposition rate () for all individuals in the same group and environment are provided. Decay rate was greatest during gas production and expulsion (days 7 to 10) in all age classes, and, at this stage, individuals underwent critical body alterations, in special in subaerial and water environments. The decay process ended at the skeletonization stage, reached after 11 days in the subaerial setting, and after 28 days when specimens were buried. The analysis of decay rate in water does not provide complete information since decomposition was conditioned by the waterlogging of feathers and tissues. The correlation of age and the decay rate indicated that older individuals decayed faster during the first 6 days, before the onset of the gas phase. Also, during the early stages of the process, differences in decay rate were induced by age, while during the gas phase, variation was driven by individual factors. When skin was removed, corpses underwent rapid dehydration, which induced an exponential decrease of the decay rate. By comparison, skin tended to dampen and varied in decay rate.
A taxonomic and taphonomic study was carried out on two assemblages of microfauna from the Pliocene locality of Kanapoi in north-western Kenya, in order to understand the agent/s responsible for their accumulation and the taphonomic processes that have influenced the assemblages. The two sites, namely, Nzube's Mandible Site and the Bat Site have yielded microfaunal remains comprising largely rodents and bats. The fauna at Nzube's Mandible Site derives from the same site as the holotype mandible of Australopithecus anamensis and comprises largely murids, while that from the Bat Site consists largely bats. Characteristics of the assemblages such as the high representation of nearly all skeletal elements suggest that, although pre- and post-depositional processes caused damage to the faunal remains, overall the samples are a fairly true reflection of the original assemblages that accumulated at the sites. Further, the high representation of virtually all skeletal elements, the minimal degree of etching among the murid incisors, and the high faunal diversity, particularly at Nzube's Mandible Site, indicate that the two assemblages accumulated in situ by way of predation. Even though several predators may have been involved, the barn owl (Tyto alba) or the giant eagle owl (Bubo lacteus), are the most likely accumulators of the two assemblages.
This paper presents the results of a study of decomposition and disarticulation of kangaroo carcasses in caves at Naracoorte, South Australia. Carcasses were placed in two caves and observed over a period of nearly three years. Decomposition progressed rapidly within the caves with almost immediate infestation by blowflies and fungi. Invertebrate activity had ceased by 28 months; however, fungal colonisation continued for the course of the study period. Decomposition, skeletonisation and disarticulation were complete by 600 days. The results suggest that temperature and humidity play an important role in decomposition as this directly affects the activity of invertebrate and fungal decomposers. The position of the carcass within the cave influences the degree of dispersal of remains in pitfall caves. Disarticulation sequences for the experimental carcasses compare with those for kangaroo skeletons on the land surface in semi-arid South Australia, suggesting that regardless of environment, anatomy is a key factor in determining disarticulation sequence. The results of this study have applications for the assessment of stratigraphic integrity and reworking of fossil deposits in caves at Naracoorte and elsewhere.
On the High Plains of North America the harvester ants Pogonomyrmex occidentalis and P. owyheei build large gravel covered nest mounds in which artifacts and small fossils are frequently deposited. The effect this mound building behavior has on the archaeological record has received little attention and has generally been viewed as restricted to subsurface tunneling disturbances. Initial experiments highlight the surface foraging behavior of harvester ants actively transporting artifacts during mound construction and maintenance. Non-food related foraging behavior was investigated by placing glass beads around ant mounds in various patterns to evaluate foraging distance, direction, density and distribution effects. Ants were observed to forage a maximum of 48 m from the nest but the majority of foraged materials were returned from within 20 m, regardless of density, direction, or distribution differences. Of 812 individual mounds recorded during an extensive landscape survey, 134 contained anthropogenic debris. Additionally, mounds tend to form near disturbed and eroding soils which enhance the opportunity for ants to acquire actively exposed artifacts during foraging for mound construction material. These characteristics of harvester ant foraging effectively create highly visible loci of small artifact concentrations that are otherwise poorly represented by traditional pedestrian surveys. Understanding the taphonomic signature of harvester ant artifact transport should aid in refining interpretations of artifact patterning observed in archaeological contexts.
Home Sharing: Carnivores in Anthropogenic Assemblages of the Middle Pleistocene.
Jordi Rosell, Ruth Blasco.
Keywords: MIDDLE PLEISTOCENE, IBERIAN PENINSULA, CARNIVORES, GRAN DOLINA, BOLOMOR CAVE
[+info] VOLUME 7. ISSUE 4. 2009 (3 issue)
The Middle Pleistocene is a period with a great variability of carnivores. Different species of big cats, hyaenids, bears and canids are common in faunal lists of anthropogenic assemblages. This phenomenon raised a discussion about the relationships between carnivores and hominids. This paper aims to provide data to understand the presence of carnivore remains or the elements generated by them in Middle Pleistocene anthropogenic assemblages. We analyze two Spanish sites for this specific work: TD10-sup of Gran Dolina (Sierra de Atapuerca, Burgos) and Level XII of the Bolomor Cave (Valencia, Spain). The origin of both accumulations is due to the predatory activities of humans and carnivores´ incidence is very low. The main objective of this study is to determine the role of predators in these accumulations and to evaluate their relationship with human communities. The anatomical representation of carcases, the age of death of animals, the identification of anthropogenic marks and tooth marks, and the morphology of the latter suggest the existence of marauding small scavengers. These animals visited the cavities once abandoned by hominids. From this perspective, we think that there are not direct relationships in the form of interaction between both biological entities.
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