BLACK BEAR DECOMPOSITION - WEEK 1

We have been observing the bear, collecting insects, and rearing maggots for a week now. We have watched the bear and the insects change through time.
The bear has gone through phases of being very stiff and rigid to becoming more 'relaxed' as decompostion progresses. The stench is overwhelming. The skin has begun to slough off the body due to the action of the 10's of thousands of maggots present.

The insects have changed as well. The first arriver was a green bottle fly (Phaenicia sericata), a very common blow fly. They laid eggs quickly. The black blow fly (Phormia regina) came next, followed by cheese-skipper (Piophilidae) and black scavenger (Sepsidae) flies.

See our Forensic Insect Photo Atlas for some pictures of these flies:
http://www.cmnh.org/site/ResearchandCollections_InvertebrateZoology_Research_ForensicEnt_ForensicPhotoAtlas.aspx


We have hundreds of maggots being reared on beef in a small enclosure about 100 feet from the bear. We keep the insects there so the stench of decaying meat doesn't foul our lab and generate protests from colleagues. We also keep them in an outdoor enclosure so we can easily follow their growth and development at the same temperatures the bear and its insect community are exposed to.



HERE ARE SOME PHOTOS OF THE FIRST WEEK OF DECOMPOSITION:



22 May 2007: Laura Bock, a student of the Cleveland Institute of Art and a Museum summer intern, erects an exclosure around the bear to deter large scavengers. We thank the Kirtlandia Adopt-A-Student program for providing funds for Laura and her work!

22 May 2007: The bear during its first hours exposed to insect activity. Note that it is in a cage (or exclosure) to prevent large scavengers such as coyote from disturbing the study.

22 May 2007: The bear in its exclosure. It is positioned at the edge (or ecotone) between an open goldenrod field and a forest fragment composed mainly of wild black cherry. This is fairly typical habitat for black bear.

24 May 2007: The first colonizers... Blow flies arrived quickly and laid eggs. Within two days, we noted these maggot masses in the nostrils. There were also maggots in the mouth and around the anus. Openings to bodies and carcasses are the first places flies lay eggs. The tissue is soft, and there is moisture there that prevents the soft-bodied maggots from desiccating...

25 May 2007: The debris on the bear is just leaf-fall. Note the sticky trap next to the paw. It is just a cardboard sheet with a sticky material on it to capture flies. Each of those dots on the sticky trap is a fly! Hundreds were attracted to the bear. The sticky trap gives us an idea of what fly species are attracted to the bear. New traps are placed out daily...

26 May 2007: It doesn't look like much has changed since yesterday, but note the slight change in postion of the head to the photo above. Most of the action is taking place within the head and anus, out of view. The head is shifting because the decomposition of the musculature, as well as its consumption by maggots, will cause the animal to "relax" somewhat.

28 May 2007: Again, not much looks too different, but note the tail is pulling back from the body due to maggot action. The whitish material seen under the chin is frass, or insect excrement (yes, maggots poop) from those feeding in the nostrils and inside the mouth.

28 May 2007: Six days into decomposition, things are really moving... The skin is sloughing from the body. A huge maggot mass has accumulated around the anus/genitalia/abdomen. The nostrils, mouth, and ears are stuffed with blow fly maggots. Hundreds of flies (families Calliphoridae, Muscidae, Piophilidae, Sepsidae, and Phoridae) are still active. Many of the maggots are approaching full growth. See our blow fly life cycle diagram at:

http://www.cmnh.org/site/ResearchandCollections_InvertebrateZoology_Research_ForensicEnt_ForensicBlowfly.aspx

Note that the daytime temperatures are reaching the high 70s to mid 80s F, while night temps have dropped as low as 50F.

28 May 2007: Note that the skin is sloughing off the body below the chin.

28 May 2007: This is the maggot mass that was generated around the abdomen at day six. A blow fly can lay 100 eggs or more. When these maggots mature in a few days, they will wander off the carcass to find a safe place in the soil to form the pupal stage. Once they do that, we suspect it will take some 5-7 days before an adult fly is liberated from the pupal skin (or more technically, the puparium).