WHY AND HOW WE STUDY DECOMPOSITION

Why we are doing this...

We will observe and record the comparative decompositional patterns of pigs (standard animal used in decomp studies) and a black bear (Ursus americanus). While swine is often used to simulate human decompostion (during forensic research), bears are physically different than pigs (fur, size, body cavity, etc.) and may have different decompositional patterns and insect visitation dynamics. These data may then be applied to any future cases involving poaching of black bear in this part of the US. At the conclusion of the study, the bones of the animals and the insects collected will be accessioned into the CMNH collections.

How do we do this?

1. MAKE DAILY OBSERVATIONS

We record visual observations and photograph the carcass daily. We note insect activity, and the degree of decomposition for that day. We also record hourly temperature which we can use to calculate insect growth rates.

2. COLLECT INSECTS

We collect representatives of the insect community daily during the first few weeks. An insect succession will take place - in other words, the insect species on the carcass will change through time. By noting the insects present, we can document the succession which will possibly provide some data for determining how long a carcass has been dead.

Maggots are the most important insect specimens, particularly those of blow flies (family Calliphoridae). They are attracted to carcasses (and human corpses) very quickly, often within a few minutes or hours following death. They begin to lay eggs, and the maggots that hatch from the eggs provide a wealth of information of time since death (also known as postmortem interval).

We also conduct rearings of immature insects, particularly maggots, to the adult stage to facilitate their identification. Adult insects are relatively easy for the trained expert to identify, but maggots can be challenging. Having adults is handy... We can also study the growth and development of the flies collected. As we can expect several species of blow fly to be present (and each has its own development rate), a species-level identification is needed.

3. ANALYZE THE DATA

Basically, at the end of the decompositional process where only a skeleton remains, we can pull together our data to show the insect succession and the rates of development for the species present. With these data, a wildlife official can show us a poached bear and if insects are present, we can give an accurate estimation of the time of death. This can provide important supporting information during poaching investigations.