The Die-Off On James Island

Excerpt from the book The Hidden Dimension by Edward T. Hall, Chapter II: Distance Regulation In Animals

About fourteen miles west of the town of Cambridge, Maryland, and less than a mile out in Chesapeake Bay lies James Island, approximately half a square mile (280 acres) of uninhamited land.

In 1916 four or five Sika deer (Cervus nippon) were released on the island. Breeding freely, the herd built up steadily until it numbered between 280 and 300, a density of about one deer per acre.

At this point, reached in 1955, it was apparent that something would have to give before too long.

In 1955, Christian began his research by shooting five deer for detailed histological studies of the adrenal glands, thymus, spleen, thyroid, gonads, kidneys, liver, heart, lungs, and other tissues.

The dder were weighed, the contents of their stomachs recorded, and age, sex, and general condition, as well as the presence or abscence of deposits of fat under the skin, in the abdomen, and between the muscles, were noted.

Once these records were made, the observers settled down to wait.

In 1956 and 1957 no change occurred. But in the first three months of 1958, over half of the deer died, and 161 carcasses were recovered.

The following year more deer died and another drop took place. The population stabilized at around eighty. Twelve deer were collected for histological study between March 1958 and March 1960.

What was responsible for the sudden death of one hundred ninety deer in a two-year period?

It wasn't starvation, because the food supply was adequate. In fact, all of the deer collected were in excellent condition , with shining coats, well-developed muscles, and fat deposits between the muscles.

Carcasses collected between 1959 and 1960 resembled those taken in 1956 and 1957 in every outward respect but one. The deer taken after the population collapse and stabilization were markedly larger in body size than those taken just before and during the die-off.

The 1960 bucks averaged 34 per cent heavier than the 1958 bucks. Does taken in 1960 were 28 per cent heavier than the 1955-57 does.

The weight of the adrenal glands of the Sika deer remained constant from 1955 to 1958, during the period of maximum density and die-off.The weight decreased 46 per cent between 1958 and 1960.

In immature deer, who formed a large proportion of the casualties, adrenal weight dropped 81 per cent after the die-off.

There were also important changes in the cell structure of the adrenals that pointed to great stress, even in the survivors.

While two cases of hepatitiswere discovered , it was thought that these were a result of decreased resistance to stress due to overactive adrenals. In interpreting Christian's data, it is important to clarify the significance of the adrenal glands.

The adrenals play an important part in the regulation of growth, reproduction, and the level of the body's defenses. The size and weight of these important glands is not fixed but responds to stress.

When animals are too frequently stressed, the adrenals, in order to meet the emergency, become overactive and enlarged. The enlarged adrenals of characteristic cell structure showing stress were therefore highly significant.

An added factor which undoubtedly contributed to stress was the fact that freezing weather in February of 1958 prevented the deer from swimming to the maninland at night, as was their custom, a journey which afforded at least temporary respite from crowding.

The major die-off followed this freeze.

Lack of relief from confinement, combined with cold, which is also known to cause stress, may have been the last straw.

Summing up at a symposium on crowding, stress, and natural selection in 1961, Christian stated:

"Mortality evidently resulted from shock following severe metabolic disturbance, probably as a result of prolonged adrenocortical hyperactivity, judging from the histological material. There was no evidence of infection, starvation, or other obvious cause to explain the mass mortality."