Abstract

The American Alligator has been used in farming and research. but techniques for egg incubation and captive rearing have not been clearly defined. This project utilized three nesting egg incubation media: 1) sand; 2) sand and vermiculite; 3) straw. Incubation temperature was maintained at 310 ± 2°C and humidity levels were at near saturation by misting of eggs daily with tap water. Medium number I (sand) permitted optimum growth. The development of embryo was followed externally by examination of membrane growth at about day 5, 10, 14, 19, 32, 39, and 45. Hatchlings were toe tagged, weighed, measured and placed in 52"L x 28"W x 18"D polypropylene tanks. The tanks were tilted so that 1/2 of the deck area was covered by water and room temperature maintained at 31 ± 3°C. A heat lamp provided supplementary heat. Growth was monitored by periodic measurements of lengths and weights. Feed consisted of 60Z whole eviscerated fish and 40% chicken liver supplemented with vitamin and mineral mixture. Protein utilization was optimized by supplementing amino acids thus preventing development of visceral gout. Common disease problems observed in hatchlings alligators are retained yolk, nutritional diseases, and stress induced bacterial diseases (HAS).

Introduction

Because of an increased need for non-mammalian animals in medical research and the growth of alligator farming, better methods for the incubation of eggs and rearing of alligators within a research environment were investigated. Three media were tested to determine a more suitable nesting medium than straw. Incubation techniques were similar to those currently used by alligator farmers (2). Tanks for the hatchling were similar to those in use by nearby alligator farms. Feed additive and supplemental heat were used to improve growth and control disease.

Materials and Methods

A total of 149 alligator eggs were collected in the wild by the Florida Fish and Game Commission. Fitty tour (54) eggs from three clutches were randomly chosen and assigned to 9 groups each containing 6 eggs. Three media were tested 1) autoclaved sand; 2) autoclaved sand and vermiculite in a 50:50 mixture; 3) untreated straw. The groups were used to test each media. Media were placed in 14 1/2 1. x 9"W x 5 1/2D polycarbonate boxes. The eggs in media #1 and 2 were covered with angel hair to retain moisture. Medium #3 woo placed on a screen above water in the box and the eggs were covered with dampened straw.

All nest boxes had individual thermometers and were covered with aluminum foil to maximize heat and moisture retention. The nest boxes were placed randomly in an upright Freas 815 Low Temperature Incubator (GCA Precision Scientific, Chicago, Illinois). The temperature within the incubator was maintained at 310 ± 2°C. Humidity was maintained at near saturation by daily misting, utilizing an atomizer container water.

Embryonic bonds were measured at three reference points on the band approximately every 5 days. Eggs having bands which did not grow or degenerating bands were eliminated from study at hatching time. Upon hatching, the alligators were identified by means of two Monel Metal Self-Piercing 01 tags (National Band and Tag Company, Newport, KY) placed in the webbing of the rear feet. The hatchlings were weighed, measured, divided into two groups and placed into 52"L x 28"W x 18"D polypropylene tank. The tanks were tilted, allowing one-half of the deck area to be covered by water.

Room temperature was maintained at 31 ± 2°C. Supplemental heat was provided by means of infrared heat lamps placed over the dry area of the tanks. The hatchlings were fed a measured diet of ground 60% ground whole eviscerated fish and 40% chicken liver purchased from local vendors. Diet was supplemented with a vitamin and mineral mixture and a mixture of amino acids prepared in the investigators lab. Before placing food in the tanks the tanks were allowed to drain, thus enabling the measurement of uneaten food, after the allotted one hour feeding time. After the removal Of unconsumed food the tanks were cleaned.

Bimonthly the hatchlings were weighed and measured. Growth rate was determined in inches/day x 1000 and condition was 3 W/L x 1000.

Results

Hatch rate and 212 day survival, growth rate and condition of hatchling alligators from eggs incubated in the three media are shown in Table 1.

Table 1. Hatch rate survival, growth rate and condition of hatchling alligator. from eggs incubated in three test medias

It was discovered with additional heat from infrared heat lamp that the hatchlings food consumption increased (Table 2).

Table 2. Effects of Heat Lamp on Food Consumption

Discussion

Artificial incubation techniques for alligator eggs previously reported (2,3) utilized straw as the nesting medium with the eggs maintained at approximately 31°C and the relative humidity approaching 100%. In the present study send and sand vermiculite 50:50 by volume were tested to provide a medium that was easier to handle and could be sterilized to assist in disease control. Vermiculite was added to sand to provide better retention of moisture near the eggs. Temperature and relative humidity In the incubator were kept at levels previously reported as satisfactory (2,3). Incubation techniques have been reported to determine the sex of the hatchling as well as its performance (growth rate, condition and survival, etc.) (1,3).

Deaths and lagging animals among farm-raised hatchlings are believed to average approximately 20%. Techniques used in the present study results in only one death among the twenty-five animals in the study group. Our results also indicate that sand or sand and vermiculite are as good as straw as nesting media and the hatchlings have improved survival and performance.

References

1.  Joanen, Ted and Larry McNease. Incubation of Alligator Eggs. Proceedings FirstAnnual Alligator Production Conference. pg- 117-126, 1981.

2.  Godwin, Frank. Incubation Techniques used by Florida Alligator Farmers Association Members in 1991, Proceedings 2nd Annual Alligator Production Conference. pg. 34-37, 1982.

3.  Ferguson. Mark W. J. The Application of Embryological Studies to Alligator Farming. Proceedings First Annual Alligator Production Conference. pg. 129-144, 1981.