Documentation

Introduction

The Snake T-maze is used to examine spatial learning, memory and decision making in snakes. It is an adaptation of the conventional T-maze which is used in assessing learning and memory in rodents. The Snake-T maze is divided equally into two halves: A conventional T-maze is constructed in one half while the other half serves as an acclimation area. The Snake T-maze allows exploration of snake behaviors based on their exploratory traits, memory, and decision-making abilities. The Snake T-maze can also be modified into an open area which can be used to assess cognition and other behavioral processes.

Snakes are predatorial animals that have excellent chemosensory abilities (Schwenk, 1995) which plays an important role in locating mates, communal shelters and hibernacula. Studies have shown that snake social behaviors rely on conspecific chemical cues (Gillingham, 1987). Experimental protocols using the T-maze take advantage of this conspecific chemical cue reliance to evaluate a range of exploratory and social behaviors as well as learning and memory behaviors. Conspecific chemical cues are usually introduced in the maze either by allowing the animal to slitter on the path to create a chemical cue trail or by holding the conspecific in the choice areas. Apart from using conspecific cues, other cues such as using a prey animal can also be used to evaluate foraging behaviors. The T-maze can also be used to evaluate the effects of different treatments such as chemosensory alterations, pharmacological manipulations and brain lesions on the snake’s learning and memory abilities.

T-mazes and its variant, the Y-Maze, are a popular choice for learning and memory research across different species of animals. Some of these variants include the rodent Y- maze, the rodent T-maze, the zebrafish Y-maze, the zebrafish bifurcating T-maze, the pig T-maze, and the bat Y-maze.

Apparatus and Equipment

The Snake T- maze consists of acrylic, open-top enclosure measuring 150 x 75 x 120 cm. The arena is divided into equal halves measuring 75 x 75 x 120 cm using a removable partition. One half of the arena in an open area that serves as the acclimation arena while the other half houses a T-maze. The start arm of the T-maze measured 75 cm in length and can be entered from the acclimation area via a removable door. The choice arms are perpendicular to the start arm and are equal in length extending parallel to the arena wall (75 cm). The T-maze walls are 6 cm tall, and the arms are 6 cm wide. In addition to the removable walls and doors, the apparatus also comes with hide boxes that measure 25 x 25 x 4 cm.

Training Protocol

Clean the apparatus thoroughly before starting a trial and in between trials using detergent to reduce contamination. Appropriately light the maze arena. A tracking and recording system such as the Noldus Ethovision XT can be used to assist with observations.

Habituation and Pretraining

Place the snake in the empty half of the testing enclosure and allow it to acclimate for 24 hours. Following acclimation, trials can be initiated immediately.

Snake T-maze task

Place the cues in the maze. Open the entrance of the maze and allow the subject to enter the maze from the acclimation area. Allow the subject to explore the maze and choose which arm of the maze to enter. Remove the subject from the maze when an arm has been chosen or 24 hours have passed. Protocols can vary depending on the experiments.

Evaluation of foraging behaviors of timber rattlesnakes

Clark (2007) tested the foraging behaviors of snakes based on conspecific chemical trails in a Snake T-maze. Sixteen Snakes (8 males and 8 females) of species Crotalus horridus were used as the test subjects. Subjects fasted for 4 weeks prior to being tested. The experimental set-ups included different combinations of chemical cues or their absence. Chemical cues were obtained from unrelated, same-sex conspecifics that were either starved (NF) or fed mice (F) for 4 weeks. It was observed that the timber rattlesnakes chose the conspecific chemical trail regardless of the cue being obtained from fed or non-fed donor in the conspecific trail versus blank substrate set-up. When tested for F versus NF conspecific chemical trail preference, no significant difference in trail choice was observed. The arena was transformed into an equally divided open arena to assess the role of public information in foraging behaviors further.  When presented with ambush site choice based on F versus NF, snakes spent more time in the side of the F conspecific cue. Thus, based on the data, the timber rattlesnakes were observed to use public information in their foraging behavior.

Data Analysis

The following parameters can be observed on a Snake T-maze:

• Frequency of entry into the right arm
• Frequency of entry into the left arm
• Time spent in the right arm
• Time spent in the left arm
• Frequency of correct arm choice
• Frequency of incorrect arm choice
• Time spent in either half of the enclosure

Strengths and Limitations

Strengths

The Snake T-maze is used to test learning, memory, and decision making in snakes. It can also be used to evaluate mating behaviors, foraging behaviors, and other exploratory behaviors. The maze allows the application of different experimental protocols. Modifications such as removal of the partition to create an open arena or inclusion of guillotine doors allow the maze to be easily adapted for different experiments. The Snake T-maze allows for easy acquisition and interpretation of data. It is easy to operate and produces reproducible results. The absence of stressful stimuli allows for better observations of behavior and working memory as the subjects perform the task.

Limitations

Factors such as age, gender, and strain of the subjects may contribute towards their task behavior. Subject’s explorative drive greatly influences experimental results. Unnecessary stimuli may affect the way the subject performs the task. Chemical cues from conspecifics of the same gender or relation may affect chemosensory behavior related to courtship or kin aggregation. Withholding of food from test subjects greatly influences their behavior to perform the task.

Summary

• The Snake T-maze is used to test learning, memory, and decision making in snakes.
• The Snake T-maze is an adaptation the conventional T-maze. The maze design includes two arenas: T-maze and acclimation area.
• The Snake T-maze can easily be transformed into an open arena.
• The Snake T-maze can be used to assess behaviors associated with finding mates, shelter, hibernacula, and
• Exploratory behavior of subjects may affect the results of the experiment.

References.

1. Clark, R.W. (2007). Public information for solitary foragers: timber rattlesnakes use conspecific chemical cues to select ambush sites. Behavioral Ecology, 18(2), 487-490. doi: 10.1093/beheco/arm002
2. Gillingham J.C. (1987). Social behavior. In: Seigel RA, Collins JT, Novak SS, (Ed.), Snakes: ecology and evolutionary biology. (pp. 184–209). New York: Macmillan.
3. Schwenk K. (1995). Of tongues and noses: chemoreception in lizards and snakes. Trends Ecol Evol. 10(1), 7–12.