Decomposition of a small hawk is a fast process...

1 October 2007: The past few weeks have shown us a few key points about the decomposition and the insect succession on a small raptor.

a. The small (<>

b. Flies will lay eggs on this small carcass very quickly. Within a few minutes of positioning the cooper's hawk, we had green bottle flies laying eggs.

c. The fly maggots will hollow out the body and skull, then migrate off.

d. Insect succession is quick, with 'later arrivers' coming quickly. These include the sap beetle Omosita colon, sphaerocerid flies, and others.

e. Because of the fast succession, the forensic use of insects will be the most useful during the first 1-2 weeks, but after that the quick drying prevents an accurate estimation, except for maybe a minimum time of death.

The photos below show decomposition from 14-28 September 2007:

Decomposition of a migratory hawk

In terms of avians being poached, hawks are often shot during migration in September. With the help of CSU graduate student Krystal Hans, and CMNH Ornithologist Dr. Andy Jones, we placed out a cooper's hawk (Accipiter cooperii) for decomposition. The photos below document the first couple of hours of activity.

13 Sept. 2007: This cooper's hawk was found dead and provided to the Museum. We will allow it to decompose for 4-6 weeks, study the insect faunal succession, and then provide the bones to the Museum's osteology collection.

13 Sept. 2007: Two hours post-exposure, green bottle flies swarmed the bird, laid eggs inside a wound on the ventral area of the carcass, and laid eggs underneath the carcass between the feathers and the ground.

13 Sept. 2007: Krystal collecting blow fly eggs (green bottle flies: Calliphoridae) from the cooper's hawk carcass.

FINAL COLLECTIONS

We have officially completed our collections from the bear and the pig. The animals were well-skeletonized, although the thick hide of the bear remained in large part. The bear still supported some invertebrates in some number (Omosita, Necrobia, misc. staphylinids, Stearibia nigriceps). Interestingly, the soldier fly Ptecticus sp. (recorded earlier in the summer) was also present in the adult stage. Its forensic importance is still unknown.

Our conclusions are that 1) a similar fauna attacks large mammals and humans alike, and 2) the decomposition of the bear may be slowed by a variety of factors including the thick hide and fat layer. Further, Lucilia illustris was the first arriver followed quickly by Phormia regina, which is expected. There were three distinct waves of maggot movement off the bear, one off the pig.



13 Sept. 2007: Graduate student Krystal Hans assists with invertebrate collections off the bear carcass.

13 Sept. 2007: The final stage of decomposition in the pig - dry remains.

Later arrivers...

19 July 2007: Upper left, Stearibia nigriceps, a piophild fly; Upper right, Leptocera sp., a minute dung fly of the family Sphaeroceridae; Lower left, Nicrobia violaceae, a beetle of the family Cleridae; Lower right, another fly of the family Piophilidae, Prochyliza.

The flies and beetle illustrated above are common on both the pig and the bear carcass. They illustrate nicely the concept of change through time as they come after the initial wave of blow flies and house flies. They are adapted to the drying conditions encountered on an aging carcass, and take advantage of the areas of carcasses touching the ground. Here, it is moist, dark, and protected.

In terms of our use for determining a postmortem interval, these species are not as useful as blow flies. But, they their presence or absence can be useful. They indicate a change in the carcass, and are part of the insect succession.

All four species above are generalized scavengers of decaying animal tissue in the larval stage. The adults seen above really are there to mate and lay eggs. The adults do little if anything to aid decomposition directly.

The Ecological Players in the Decompositonal Game

15 July 2007: Upper left, Phormia regina, the black blow fly; Upper right, Lucilia illustris, a green bottle fly; Lower left, Fannia canicularis, the lesser house fly; Lower right, Sarcophaga sp., a flesh fly.

OK, not much has been happening on the pig or bear carcasses. So we shall take a detailed look at some of the insects obtained during the course of this investigation.

The flies illustrated above are some of our most informative and/or interesting flies on the decomposing bear and pig. The two above represent our predominant blow flies. The green bottle fly (Lucilia illustris) is one of several species of green bottles we encounter regularly on carrion here in northeastern Ohio. It is often the first to arrive, and based on our sweeping of adult flies off the carcasses, larval collections off of the carcasses, larval collections of the wandering masses of maggots, and our rearings, we found that L. illustris was indeed the first arriver.

The black blow fly (Phormia regina) arrived and developed concurrently with L. illustris, but developed a little more slowly. Lucilia flies were only present on the carcass for a short while, followed by numerical domination by the black blow fly.

The lesser house fly (Fannia canicularis) was interesting. Not an early arriver, nor very predictable in its arrival time, it is not a precise predictor of time of death. However, the literature suggests it arrives when fecal material in the guts of the carcasses are exposed. Our observations show that this is not necessarily the only time it arrives and deposits eggs. We found that the adults lay eggs underneath the dry carcasses on the vegetation, and the larvae develop nicely on the blackened, decomposing grasses fouled by mammal decomposition. Further, we obtained eggs, larvae, and pupae of this species when we exposed raw beef.

Lastly, Sarcophaga or flesh flies are often times present in reasonable numbers on carcasses. I reared flesh flies off a dead shrew near this field site recently, and it was the only taxon present on the small carcass. We have so far recovered no individuals from any of our efforts. The lack of flesh flies is both interesting and not easily explained.

Next post, we shall provide information on more fly species taken on our pig and bear carcasses.

A tale of two carcasses...

2 July 2007: We are still keeping an eye on the bear periodically. We lift the legs, head, and torso to accumulate a collection of cryptic beetles and their larvae. This will allow us to document relatively long-term succession of insects on the carcass. During this phase of deep dessication, we collect beetles and sweep for flies approximately weekly.

2 July 2007: The pig, like the bear, is also in the dry phase of decomposition. The underside is still moist, and maggots are present (see below).

2 July 2007: This morning, just a few hours short of exactly 1 week into decomposition, we had a mass exodus of maggots from underneath the carcass. The grasses and weeds obscure the view, but in the photo above you can make out the larvae clearly. The smaller carcass supported fewer numbers than the large bear (a 119 pound difference), but there were thousands of maggots moving into the undergrowth to burrow into the soil for pupariation.

3 July 2007: After the movement of maggots off the body yesterday, little activity is observable.

3 July 2007: The effects of maggot feeding... The larvae consume the carcass down to the bone, exposing the drying internal organs and pave the way for a dry phase of decomposition. This is where beetles, sepsid flies, and piophilid flies become the dominant players.

4 July 2007: We're pretty much in a phase where, like the bear, decomposition will progress very slowly. We'll continue to collect, but not daily. We will collect beetles on our under the carcass and sweep for flies 1-2 times per week. It is very overcast today, and rain appears to be iminent. That being so, we may see a resurgence in fly activity. If it does indeed rain, I'll head out check again today. The moisture will make some of the tissue soft again, and perhaps we'll have a second wave of blow flies. It really depends on how much rain we get, if any...

PIG DECOMP: Baseline data for northeastern Ohio

25 June 2007: While we are doing the bear decomposition study, we decided to put a domestic pig out in an area nearby. Laura Bock above has just placed the carcass out on the afternoon of 25 June. Pigs are often used during studies of forensic entomology because the body size, body cavity size, percent hair coverage, and other characters make pigs very similar to humans in terms of decompositional patterns. We will be gathering insect succession data, and keeping track of fly development to better hone our information on local insect forensic indicators.

25 June 2007: Like the bear, we placed caging around the pig to keep out large scavengers. We want to keep the bones to add to the Museum's osteology collection. Note that the frame of the cage has short legs, creating a space for wandering maggots to egress at a later date.

25 June 2007: Things happen fast at summer temps. Two hours after placement, we already have hundreds of female flies laying eggs (ovipositing) on the pig around the orifices of the head and anus.

26 June 2007: Less than 24 hours after placement, eggs have hatched and maggots are making fast work of the snout. Note the light area under the chin is actually an egg mass. The eyes, mouth, and nostrils are choked with 10's of thousands of maggots. The blow flies Lucilia illustris (a green bottle fly) and Phormia regina (the black blow fly) constitute the majority of these maggots.

27 June 2007: Two days into decomp the head is being rapidly consumed. The body is showing considerable swelling from bacterial gasses in the abdomen. Carrion and rove beetles are present hunting maggots.

28 June 2007: By day three the maggots are getting large and breaking the body down at a horrendously fast pace. The smell is awful, and the liquids of putrefication are staining the ground black. The maggot mass temperature, like with the bear, is 18 degrees C above ambient.

29 June 2007: By the fourth day, many maggots have matured and are leaving the carcass. The masses of maggots at the head and anus have appeared to meet in the middle, as the main body cavity is greatly decomposed. We have collected many maggots in ethanol, kept many alive in breeding containers (we're still using our nearby insectary), and have swept scores of adult flies to facilitate identification. We have been taking beetle adults and larvae using forceps.

The dry phase of decomposition

29 June 2007: During this period of very slow decomposition, we do have occasional colorful visitors as shown in the photo above. This is a question mark, a type of brush-footed butterfly (family Nymphalidae). Butterflies and moths visit every so often to sip on the moisture present on or in some parts of the carcass. These liquids are going to be rich in nutrients, and help insects we normally associate with plant pollination develop energy and nutrient reserves to aid with movement and egg production.

We have witnessed and recorded a shift in the fly fauna. The dominant taxon present is the sepsid fly Nemopoda nitidula. Not much is known about this fly, although it has been associated with carrion in the past. I have taken it in carrion-baited traps, and reared it from maggots on a dead bat in a cave. Their value as a forensic indicator is presently unknown.

A month into decomposition...

23 June 2007: As you can see from the image above, not much has changed over the past week. We collected intensively yesterday, and here is the fauna:

FLIES: 3 blow fly puparia, a few adults of Phormia regina, piophilid flies (Prochyliza sp. and Stearibia nigriceps), some undetermined muscoid adults, and some maggots that are presumably the black dump fly.

BEETLES: first adult of the carrion beetle Nicrophorus tomentosus, the sap beetles Omosita colon and Necrobia rufipes, larvae of the silphid genus Necrodes, and miscellaneous rove beetles.

We are confident so far that we can apply the same data on insect development that we use on human victims to cases of black bear poaching. We still need to be careful about interpreting the faunal succession (change over time). To help with this, we are placing a pig out in the vicinity of this black bear to document the faunal succession there. That begins tomorrow afternoon (Monday, 24 June), and should last about a month. Again, the bones from the pig will be accessioned into the Museum's osteology collection.

Data from rearings

17 June 2007: Not much new happening on the bear itself. Still some small flies and carrion beetles, but with some rain this morning we observed a few black blow flies (Phormia regina) exploring the surface of the carcass.

17 June 2007: On the other hand, our rearings of insects taken from the carcass or wandering from the carcass are yielding good data! The idea is simple. Maggots are relatively challenging to identify to species. We collect maggots, but simultaneously place living ones on raw beef in containers to raise the maggots to the puparial and then the adult stage. This helps narrow the possible range of taxa represented by the maggot collections.

Our techniques are nothing special. We take some damp paper towel and in it place a cube of beef approximately 1"x1"x1". This is wrapped loosely in some aluminum foil, and this packet is then placed on top of some vermiculite or saw dust. When the maggots mature, they will wander off the meat (just like they do on the carcass) and move the saw dust to form the puparium. We have to continually check the packet, as some maggots don't go far and form a puparium in the foil. These are just removed and placed in the saw dust.

If we have maggots moving off the carcass, we collect these too, and place them in separate containers with the date and time of collection. The maggots are put into a pile of saw dust and allowed to pupate. The photo above represents the results of collecting 75 wandering maggots collected about a week ago. All appear to be Phormia regina. I placed this container in the freezer today, and will leave overnight. They will then be taken to the lab for identification and recording of data. Some representative specimens will be mounted on pins, labelled, and placed in the forensic entomology collection of the Cleveland Museum of Natural History.

Approaching the first month of decomp

15 June 2007: The majority of active insects consist of silphid (carrion) beetles hunting soft-bodied invertebrates, black dump fly maggots (predators of other maggots), various beetles interested in dry tissues, miscellaneous yet-to-be-determined minute dung flies of the family Sphaeroceridae, 3 species of Sepsid flies (Enicomira, Sepsis, and Nemopoda), and 3 species of Piophilid flies (Piophila, Prochyliza, and 1 undet. genus). Sweeping over the bear yields mostly the small flies (Sphaeroceridae, Piophilidae, and Sepsidae).

The underside of the bear is still moist. This is where the black dump fly maggots and most of the carrion beetle larvae are. We are supposed to get rain this weekend, and that could change some of the activity dynamics. For instance, maggots and beetle larvae may move to the surface, or we may get a new generation of flies hitting the carcass.

13 June 2007: At this point, insect activity is greatly slowed and our efforts include mostly sweeping small flies from the carcass with an insect net, or as Laura is demonstrating we use forceps to nab beetles and beetle larvae from the surface of the carcass. We carefully lift the legs and head to expose the moist areas under the carcass where there is still some maggot activity, and invertebrate predators are still common.

Dry Times: 5-10 June 2007

10 June 2007: Decomposition is greatly slowed... Here is what we have learned so far:

1. We had 3 major mass movements of maggots off the carcass. The middle wave had by far the most maggots (4 June). The last wave was the least dense.
2. The same insects we expect on human corposes are also found on the bear.
3. Seemingly because of the dense fur and mass of the body, decomposition progressed somewhat differently with all of the maggot movement off the carcass originating around the abdomen.



9 June 2007: Very little blow fly activity is present (maggots and adults).

7 June 2007: Today, we saw the last (third) wave of wandering maggots leave the body. Dr. Dan Palmer of John Carroll University is a computer scientist specializing in swarm behavior, a means of analyzing group dynamics and their subsequent emergent properties.

7 June 2007: Here is the last wave... The first wave was more dense than this, and the second wave from 4 June 2007 (see below) was the most dense. This last wave composed the least number of maggots moving off synchronously.

7 June 2007: Dr. Palmer noticed that those individuals that were separate from a group simply oriented themselves away from the exclosure. Those within groups were positioned haphazardly, but the mass itself made consistent progress away from the carcass. This opens up new possible questions in using swarm theory to describe wandering maggot behavior!

5-6 June 2007: Very little bug activity (relatively speaking) is present. Sepsid and piophilid flies are still active, as are some muscids. Silphid larvae are common, and nitidulid adults are abundant at this time.

14 Days into Decomp...

4 June 2007: The maggot masses are moving off of the bear. the abodomen and mouth/nose remain highly active. Nearby 'waves' of maggots are not nearly as huge as earlier observations.

4 June 2007: Our insectary. About 100 feet from the carcass, we rear immatures collected from the bear to help facilitate identification of material collected from the bear. The location of the maggots on the bear is recorded (e.g., collected from mouth, collected wandering from carcass, etc.). Live maggots are given raw beef.

Week 2: 2-3 June 2007: Huge Maggot Exodus

An incredible sequence of maggot migration...

3 June 2007: Rain has created a situation where maggots are creating large amounts of 'froth' around the edge of the bear.

3 June 2007: Maggots are moving in an enormous exodus from the bear. We began to see this to a smaller degree several days ago, but now they are grouping together in a virtual maggot swarm.

3 June 2007: A close-up of maggots on the trail...

3 June 2007: A maggot's-eye view of the exodus of the carcass. The maggots remaining on the bear are probably somewhat younger. Many early instars of blow flies are still present on the carcass. There will probably be another substantial mass movement of maggots of the carcass in upcoming days.

3 June 2007: During the study, we have been keeping track of maggot development. At the bottom is a mature maggot. Above that is a newly formed pupa (hours old), followed by a darker puparium a day or so old, followed by progressively darker (and older) puparia.

2 June 2007: In the morning, many maggots are mature and actively moving. This appears to be in preparation for a mass migration off the carcass. The stench is still horrendous, and the vegetation is dying around the bear.

2 June 2007: The first real "wave" of maggots leaving the carcass. Many maggots continue to grow an develop on the carcass. Adult flies (Calliphoridae, Muscidae, Sepsidae, Piophilidae) are still active on and around the bear.

2 June 2007: A maggot's- eye view of the trail...

31 May - 1 June: Maggot activity increasing

1 June 2007: Here is the bear, with expansive coverage by feeding maggots, 11 days into the decompositional process. What have we learned so far?

1 - There are many similar patterns seen on the bear that we see in pig or human decomposition, such as flies laying eggs on or within orifices (mouth, nose, anus, etc.), early activity by green bottle flies of the tribe Luciliini (e.g., Phaenicia) followed by the black blow fly (Phormia regina), beetle activity occurring slightly after flies arrive, and the subsequent arrival of small flies after blow flies have 'conditioned' the carcass (e.g., Piophilidae, Sepsidae).

2 - There is a slight delay in maggot activity compared to humans or pigs. This may be for two reasons: a) the expansive coverage of fur, and/or b) the freezing of the carcass prior to the study may have altered the tissues enough to make them less-than-ideal for attracting egg-laying flies.

3- At about day 10, herbaceous plants (e.g., Virginia creeper) near the bear begin to turn brown when decompositional fluids saturate the soil.

1 June 2007: Maggot activity on the head has literally exploded.

1 June 2007: A close-up of the maggot mass centered in the mouth and nose. When we took outside temperature readings it was 27.5 degrees C. Placing the bulb of the thermometer into any of the maggot masses gave a reading of 46.0 degrees C - nearly 20 degrees warmer!

Maggot mass temperatures are important. They occur from the normal metabolism of feeding maggots (movement, feeding, digestion, etc.) and warm the carcass. This increased temperature probably helps to accellerate maggot development.

31 May 2007: The maggot mass covers most of the body. Fur is being deposited by maggot action in a circle around the bear.

31 May 2007: The head orifices are still a key point of maggot activity.

31 May 2007: Our observations show that the migration of maggots from the body (to find a safe place in the soil to form the pupa, or in flies pupariate) occurs most heavily early in the morning. By mid day, when temperatures are high, dessication is possible, and visual predators are abundant, the migrational activity is at its minimum. This photo was taken about 8:00AM.