Hot or Cold? :
Raising Snakes for Optimal Growth
Question:
After a single meal, do Honduran milk snakes (Lampropeltis triangulum hondurensis) lose weight more rapidly at a warmer temperature?
Abstract:
This experiment was designed to answer this question by utilizing temperature as a variable. Temperature was used as a variable because it is reported to be correlated to the efficiency of snakes’ digestion. This experiment measured the weights of two milk snakes: one in a warmer cage and one in a cooler cage. The snake in the warmer cage lost weight more quickly than the snake in the cooler cage after a single meal. The results of the experiment proved to be ambiguous due to several factors, but nevertheless this experiment offers an accurate way to assess the effect of temperature on snake growth.
Introduction:
Snakes are ectotherms. Being “cold-blooded” affects how snakes process food because chemical processes involved in digestion are reported to speed up or slow down depending on temperature. Because snakes do not generate their own heat, they must depend on either altering their behavior (e.g. curling up or shivering) or else moving to a different environment (e.g. basking in the sun) to regulate their body temperature. The most relevant portion of the body here is the stomach, a j-shaped organ. The majority of food digestion occurs there because the cells of the stomach secrete digestive enzymes and gastric juices that breakdown proteins. After swallowing their prey, snakes will often move to warmer places to raise their body temperature, presumably to speed up digestion.
Snakes lose weight by moving around and excreting. Snakes are more active at higher temperatures. Digesting food more efficiently results in maximizing the calories, a measure of energy, taken in per food item, while digesting more quickly results in excreting sooner. Thus it can be predicted that if a snake at a higher temperature utilizes the calories of a meal more efficiently, it will be more active and lose weight more quickly after a single feeding. It should be able to complete a feeding cycle more quickly and thus grow faster and gain more weight over the long term.
The results from this experiment are important to herpetoculturists. A common technique to increase a snake’s growth is to “overfeed” a young snake. The practice of overfeeding in order to breed snakes at an earlier age is very common in commercial reptile breeding and is harmful to the snakes. Overfeeding can shorten a snake’s life span. By keeping the snake at an ideal temperature a breeder should be able to safely increase the rate of growth and thus, allow the snake to breed at a younger age more safely (although it is still advisable to breed an older, mature snake over a younger, mature snake.) Understanding the relation between weight and temperature will also enable pet owners that want their pets to remain smaller to be able to do so more safely than leaving the animal in a smaller cage or by not feeding it.
Hypothesis:
A milk snake will lose more body weight, after a single meal, in a cage with higher temperatures.
I generated my hypothesis based on the widely held assumption that snakes digest their food more efficiently at higher temperatures. I conjecture that my hypothesis will prove to be true because the milk snake’s enzymatic reactions work more efficiently at warmer temperatures, and thus, the digestion process will be hastened.
Materials:
Electronic scale (My Weigh MX-200), temperature-sensing gun (tempgun.com), frozen “pinkie” baby mice (T-Rex products, PETCO, Allston, MA), pair of similar age and weight/length Honduran milk snakes (Lampropeltis triangulum hondurensis, 8-months old), two escape-proof and comfortable cages, and one heat pad.
Methods:
First, set up each snake into a cage, with a heat pad on the bottom of one cage. Take the temperature at the cool and warm ends of each cage. Next weigh each snake in a cup by itself. Make sure that the weight of the container is subtracted from the total weight of the snake and cup. Repeat this process every day, once in the afternoon and once at night. Whenever able (i.e. when both snakes are hungry), weigh two appropriate sized meals and feed them to each snake in its enclosure. The meals used were frozen/ thawed pinkies of proportionally similar weights. Temperatures and weights were measured at the same intervals as before.
Results:
The hypothesis was supported: the snake in the warmer temperatures lost more weight than the snake in the cooler temperatures. In ten days, the snake in the warmer temperatures dropped to 94.21% of its original body weight, as compared to the snake in cooler temperatures, which lost 96.28% of its body weight. In the afternoon, the warmer side of the enclosure of the warm cage was 36.31 degrees warmer than the warm side of the cool cage and the cooler side of the warm cage was 8.29 degrees warmer than the cool side of the cool cage. At night, the warm end of the warm cage was actually 1.27 degrees than the warm end of the cool cage, and the cool side of the warm cage was only 1.92 degrees warmer than that of the cooler cage. Overall, there was a huge difference in temperature between the cages in the day, but there was almost no difference at night.
Analysis and Discussion:
The snake in the warmer cage lost a greater percentage of its initial body weight. Thus, it can be determined that the snake kept in the warmer cage lost more weight either by digesting more efficiently and/or by digesting more quickly than the snake in the cooler cage.
This experiment was only preliminary. The only way to do this project correctly is to test many snakes over many feeding cycles. Even though I took into account the varying weights from the beginning and compared the weight percentages of the two snakes, there was a problem due to a lack of time and a small number of tests. Thus, it is not determined whether the results achieved were statistically different or whether they were just normal variation. Firstly, because I was testing only two individuals, one may just have a quicker excreting cycle or one individual may be more active than the other by nature, both of which lead to more weight loss. There needed to be more replications, with more snakes and feedings to determine whether the same trends would always be achieved. Secondly, the temperature of the cages was not as drastically different as was desired because I was afraid of harming or throwing off the feeding schedule of the snake in the cooler cage, I did not lower the temperatures greatly, even though this manipulation might have resulted in more conclusive data. Also, water intake may have interfered with accuracy of the weights.
If enzyme functions and digestion processes work better at higher temperatures, then it is logical that over a longer span of time and many feeding cycles, the snake in the warmer environment will gain more weight. Each feeding cycle will be shorter, and the snake will be able to have a higher total intake of calories. However, there are several other explanations. One would be that the snake in the warmer cage excreted more. The only way I could control for this would be if I measured fecal amounts, which would be difficult to do. A second explanation would be that at higher temperatures the snake moves more and thus uses more calories. To test this I would need to measure activity rate, which would be time-consuming and difficult. Both of these factors are related to my hypothesis, but I was not able to test them specifically.
Other variables that could be studied include the species of the snake snakes, size and type of meal, and a wider variation of temperature.
Conclusion:
My hypothesis proved accurate, but not precise. The snake in the warmer cage did lose more weight. This is consistent with my hypothesis, but could have been the result of other factors. These results were inconclusive due to many factors, such as the failure to measure fecal amounts or levels of activity. This experiment is the first step to establishing a way to test the role of temperature on weight gain or loss in snakes, and thus, to safer breeding and keeping of snakes.
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