Decay and Disarticulation of Small Vertebrates in Controlled Experiments

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.