Food and Food Preferences

The cottonmouth seems to be an opportunistic omni-carnivore, because it eats almost any type of flesh that is available, including carrion. It feeds primarily upon vertebrates found in or near water; but invertebrates and eggs have also been found in the diet. The only potential prey items that seem not to be normally eaten are bufonid toads and tadpoles. I have occasionally offered tadpoles and frogs to cottonmouths, but only the frogs were accepted. But, Stanley Roth kept a cottonmouth in captivity that ate both toads and tadpoles. If tadpoles are commonly eaten, their probable rapid digestion would make identification almost impossible.

Following is a list of known foods of the cottonmouth:

Captivity: "... rattlesnake.... The same moccasin also killed and ate a smaller snake of its own species...." (Conant, 1934:382.)

Florida: "3 heron feathers, bird bone, Eumeces inexpectatus, 3 fish all under one inch in length, 1 heron egg shell" (Carr, 1936:89). According to Allen and Swindell (1948:5), "the food included other moccasins, prairie rattlesnakes, king-snakes, black snakes, water snakes, garter snakes, ribbon snakes, and horn snakes ... most of the species of frogs, baby alligators, mice, rats, guinea pigs, young rabbits, birds, bats, squirrels, and lizards ... a mud turtle ... a case of a four footer eating ten to twelve chicken eggs. The most common food appears to be fish and frogs. Catfish are included on this list...." Yerger (1953:115) mentions "an adult yellow bullhead, Ameiurus natalis ... 306 mm. in standard length [from a 63-inch cottonmouth]."

Georgia: "... full grown Rana catesbeiana, several foot-long pickerel ... dead fish if placed in a pan of water.... Natrix sipedon fasciata and Masticophis flagellum ... rats.... Toads and large Eumeces laticeps were always ignored." (Neill, 1947:203.) "Natrix, Heterodon, Kinosternon, Rana, Hyla cinerea, Microhyla, Microtine [Pitymys pinetorum]." (Hamilton and Pollack, 1955:3.)

Mississippi: "... Hyla gratiosa.... In captivity specimens have eaten frogs, mice, birds, dead fish, pigmy rattlers and copperheads. Toads ... were refused" (Allen, 1932:17). One moccasin "disgorged a smaller decapitated moccasin ... killed the day before by boys" (Smith and List, 1955:123).

Tennessee: "Beetles in one stomach; lizard (Eumeces) in another stomach; small snake (Natrix) in one intestine, and hair in another intestine. One stomach contained numerous bits of wood, up to four inches in length...." (Goodman, 1958:149.)

Kentucky: "Siren intermedia was the most abundant food item in both volume and occurrence. Frogs of the genus Rana ranked second. Together, these two items comprised almost 2/3 of the food of the snakes. The other food items were distributed among the fishes, reptiles, and other amphibians [one Rana tadpole included]." (Based on 42 samples—Barbour, 1956:37.)

Illinois: (Based on 84 samples—Klimstra, 1959:5.)

Food Item Per cent Frequency
of Occurrence Per cent
Volume

Pisces 39.3 31.9

Amphibia 36.9 26.0

Reptilia 25.0 18.2

Mammalia 30.9 17.9

Gastropoda 17.8 1.0

Miscellaneous 25.0 5.0

(Algae, Arachnida, Aves, Insecta)

Louisiana: Penn (1943:59) mentions that a "female had just eaten two young cottonmouths...." Clark (1949:259) mentions "100 specimens—34 fish; 25 Rana pipiens; 16 Rana clamitans; 7 Acris; 4 Natrix sipedon confluens; 8 birds; 5 squirrels ... catfish thirteen and one-half inches in length ... small-mouth black bass [eleven inches]."

Oklahoma: Force (1930:37) remarks that the moccasin "eats bullfrogs ... but refuses leopard frogs." Trowbridge (1937:299) writes: "several sun perch.... Another had eaten six catfish six to ten inches long ... a water snake (Natrix s. transversa) about 18 inches long ... frogs, mostly Rana sphenocephala." Carpenter (1958:115) mentions "a juvenile woodthrush.... Seven last instar cicadas ... a young cottontail." According to Laughlin (1959:84), one moccasin "contained the following items: 18 contour feathers of a duck, probably a teal; one juvenile cooter turtle, Pseudemys floridana; and a large mass of odd-looking unidentifiable material. The other cottonmouth contained one juvenile pond turtle, Pseudemys scripta...."

Texas: "... several ... feeding on frogs.... One ... found DOR was found to contain a large catfish." (Guidry, 1953:54.)

Food Item	Per cent Frequency of Occurrence	Per cent Volume
Pisces	39.3	31.9
Amphibia	36.9	26.0
Reptilia	25.0	18.2
Mammalia	30.9	17.9
Gastropoda	17.8	1.0
Miscellaneous	25.0	5.0
(Algae, Arachnida, Aves, Insecta)

Of 246 cottonmouths that I examined for food items, only 46 contained prey in their digestive tracts. Almost all of the snakes examined were museum specimens that had been collected at many places over a period of about 40 years. It was not known how long each had been kept alive before being preserved. Therefore it was impossible to determine what proportion of any population of cottonmouths could be expected to contain food. The food items were not analyzed numerically because the scales and hair, by means of which many food items in the intestine were identified, yielded no clue as to the number of individuals actually present unless several distinct kinds were found. Each occurrence of scales or hair was thus recorded as a single individual, although some such occurrences may have represented more than one animal. The contents of some stomachs were so well digested that it was difficult to determine the number of items present. As a rule only one food item was present in a digestive tract, but a few tracts contained several items of the same or different species. Three frogs (Acris crepitans) were in one snake and three hylas (Hyla versicolor) in another. Still another individual captured beside a drying pond contained six individuals of Lepomis each about three inches long and two pikes (Esox) about six inches long.

TABLE 13.—Analysis of Food Items of 46 Cottonmouths Collected in Arkansas, Louisiana, and Texas (1922-1962).

	Food Items	Number of samples in which item occurred	Percent frequency of occurrence	Estimated weight in grams	Estimated percentage by bulk
Fish		(7)	13.2		18.4
	Esox sp.	1		20
	Lepomis sp.	2		15
	Unidentified	4

Amphibians		(12)	23.0		20.4
	Scaphiopus hurteri	1		13
	Acris crepitans	2		4
	Hyla cinerea	2		12
	Hyla versicolor	1		12
	Rana catesbeiana	1		20
	Rana pipiens	3		15
	Unidentified	2

Reptiles		(15)	28.4		29.9
	Pseudemys scripta	2		15
	Anolis carolinensis	1		6
	Eumeces fasciatus	1		7
	Lygosoma laterale	2		5
	Natrix sp.	1		10
	Natrix erythrogaster	2		10
	Agkistrodon piscivorus	2		20
	Crotalus sp.	1		30
	Unidentified snakes	3

Birds		(4)	7.6		18.6
	Anhinga anhinga (juv.)	1		60
	Egret (head and neck)	1		20
	Passeriformes	2		20

Mammals		(6)	11.3		12.7
	Blarina brevicauda	1		12
	Cricetinae	5		18

Unidentified		(9)	17.0

The "unidentified" category (Table 13) refers to jellylike masses in the stomach or material in the intestine in which no scales, feathers, hair, or bones could be found. Most of the unidentifiable matter could be assumed to consist of remains of amphibians, since they leave no hard parts. If this assumption is correct, amphibians comprise about 40 per cent of the diet. Since intestinal contents were included, a volumetric analysis was not feasible. Therefore, the weight of each type of food item was estimated and the percentage by bulk calculated from it (Table 13).

Pieces of dead leaves and small sticks constituted most of the plant material found and presumably were ingested secondarily because they adhered to the moist skin of the prey, especially to fish and amphibians. However, some plant materials probably are eaten because they have acquired the odor of the prey. One cottonmouth contained a Hyla cinerea, several leaves, and five sticks from 37 to 95 millimeters long and from 12 to 14 millimeters in diameter.

Most reports in the literature state that gravid females do not feed, but four gravid females examined by me containing large, well-developed embryos also contained evidences of having recently fed. Two of them had scales of snakes in the stomach or intestine, one contained a six-inch Lepomis, and the other had hair in the intestine and the head and neck of an adult egret in the stomach.