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The Bat Y-Maze, designed in the shape of a capital Y, was utilized in an experiment by R.J. Kilgour et al. (2013) to evaluate social preferences in bats.
In this experiment, an individual “focal” bat was selected and allowed to freely navigate within a plexiglass Y-maze. Isolated “stimulus” bat conspecifics were positioned at each arm’s end of the Y-maze within stainless steel wire-mesh cages. A clear lid was used to prevent flight.
Analysis of the experiment’s data revealed that certain bats exhibited preferences for specific group-mates over others.
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The bat Y-maze consists of a three-arm structure shaped like a capital Y. It features a longitudinal start arm measuring 37 cm in length and 6 cm in width, which bifurcates into two choice arms, each measuring 30 cm in length and 6 cm in width. The maze walls stand 5 cm tall.
Modifications to the bat Y-maze can include equipping each choice arm with stainless steel wire-mesh cages (24 cm x 21 cm x 19 cm). Additionally, fans can be installed within the arms to regulate the dispersion of olfactory cues throughout the maze.
Clean the maze between trials with a mild soap solution. Appropriately light the maze. A tracking and recording system such as the Noldus Ethovision XT can be used to assist with observations.
Allow the subject to freely explore the un-baited bat Y-maze for 90 minutes.
Bait one of the choice arms with a food reward or place different stimulus cues in the choice arms. Place the subject in the bat Y-maze. Allow the subject to explore the maze. Conduct each trial for 5 minutes. Change the position of the stimulus or reward in succeeding trials. Allow the subject to rest for 5 minutes between trials.
Kilgour, Faure, and Brigham (2013) investigated the social preferences of female big brown bats (Eptesicus fuscus) using a bat Y-maze. Eight bats participated in the experiment, with each bat serving as a focal individual per trial. Two out of the remaining seven bats were randomly selected as stimulus bats and placed in cages at the ends of the two choice arms. During the trials, focal bats exhibited active interest in the stimulus bats, with none displaying nonresponsive behaviors.
The amount of time spent near each conspecific varied among the focal bats. Four bats demonstrated a preference for spending more time near one stimulus bat, despite the randomized placement of the stimulus bats. Conversely, the remaining four bats spent equal amounts of time near each stimulus bat. Among the three individuals that served as stimulus bats in multiple trials, no consistent preferences were observed by the focal bats for any particular individual.
De Fanis and Jones (1994) conducted two series of experiments using a bat Y-maze, testing female pipistrelles bats from two colonies (colony A and colony B). The bats were exposed to two odors using scent swabs from donor bats.
In the first experiment, bats were trained to differentiate between odors from two individuals within the same colony (colony A). This experiment was replicated using five different scent-receiver bats, each paired with a different donor bat, totaling 10 donors. Each scent receiver underwent 20 choice trials per day. It was observed that all bats from colony A achieved a correct choice threshold of 75% during the experiment. By day 12, all bats consistently achieved 100% correct choices, except for one female which achieved 95%.
In the second experiment, bats were tested to discern between the odor of an individual from their own colony and that of an individual from the other colony. Five scent-receiver bats from each colony were utilized. It was noted that after just 20 trials in a single day, all bats successfully discriminated between scents from their own colony and those from the other colony. Initially, each bat showed a preference for the scent from its own colony during the first trial, and this preference was reinforced in subsequent trials.
Turner, Shaughnessy, and Gould (1972) investigated individual recognition in the little brown bat (Myotis lucifugus). Thirteen mother-infant pairs were tested using a bat Y-maze with 20 trials. In each trial, two mothers were randomly placed in holding boxes at the choice arms, and the infant had to identify its mother based on auditory cues. The results indicated that infants chose their own mothers 15 times and the unfamiliar mother 5 times, suggesting successful individual recognition. However, the study did not definitively determine whether recognition relied on ultrasonic communication or olfactory cues.
Gorresen, Cryan, Dalton, Wolf, and Bonaccorso (2015) investigated the ability of wild-caught bats to detect reflected UV light under low-light conditions typical of nocturnal flight. A total of 512 individual bats representing seven species (Macrotus californicus, Myotis lucifugus, Myotis velifer, Myotis volans, Eptesicus fuscus, Corynorhinus townsendii, Tadarida brasiliensis) participated in experiments conducted using a bat Y-maze setup.
In the experiments, a pair of lamp assemblies with UV light-emitting diodes were positioned at the junction of the bat Y-maze. Prior to trials, UV light was randomly illuminated in one choice arm (treatment), while the other arm remained dark (control). Results showed that across species, the average proportion of bats choosing the UV-illuminated arm ranged from 0.64 to 0.90. All species exhibited a positive phototactic response to UV light, with more bats selecting the illuminated arm compared to the dark arm. This demonstrated that these seven bat species possess sufficient visual acuity to respond behaviorally to subtle UV light cues.
Mistry (1990) investigated the visually guided escape response of Mexican free-tailed bats (Tadarida brasilensis mexicana) concerning acoustic and visual cues, time of day, light intensity, and age using a bat Y-maze. The study involved forty lactating female bats.
In the experiment, one arm of the maze remained dark while the other was illuminated by a cave lamp. Acoustic cues were controlled using a clear Plexiglass gate placed at the end of each arm, allowing for configurations such as light/open, dark/open, light/closed, and dark/closed. Adults consistently chose the illuminated arm in the light/open and dark/closed scenarios, while showing a preference for the open arm in the light/closed and dark/open scenarios. The results indicated a preference for acoustic cues over visual cues among the bats.
Regarding circadian rhythm responses, bats displayed a significant orientation towards light throughout the day, except at 0530 hours and 0730 hours. Different light intensities ranging from 0.17 lx (low light intensity at the cave’s back) to 350 lx (bright light near the entrance) were tested. Bats exhibited a significant preference for the illuminated arm at 0.17 lx and 1.4 lx, indicating a preference for lower light intensities.
Pups from three age groups (young non-volant, older non-volant, and volant) were also tested for their response to light. Young non-volant and older non-volant pups preferred the dark arm, whereas volant pups, similar to adults, preferred the illuminated arm.
Bartonicka et al. (2009) conducted a study comparing the attractiveness of facial gland scents versus urinary scents in two bat species using an olfactory discrimination task in a bat Y-maze.
In the first series of tests, involving 5 males and 4 females of P. pipistrellus and 4 males and 4 females of P. pygmaeus (totaling 17 bats), pairs of urinary scents were used as signal targets. In the second series of tests, which included 10 males and 10 females of P. pipistrellus and 11 males and 12 females of P. pygmaeus (totaling 43 bats), pairs of facial gland scents were used as signal targets. Cotton swabs with facial gland scents or paper strips with urine were placed at the base of each choice arm before each trial.
The study found no significant differences in the exploration time between trials using urine and facial gland scents across all male and female bats or between species. Bats explored arms containing facial gland scents more intensively than those with urinary scents. Conspecific grooming was not observed near urinary scents, whereas significant grooming occurred near facial gland scents.
The study also analyzed disassortative mate choice based on olfactory signals using facial scent swabs alone. Male bats spent significantly more time sniffing the arm with conspecific female scent compared to heterospecific female scent. However, females did not show significant discrimination in their exploration and sniffing time between the arms.
The following can be observed on the bat Y-maze:
The bat Y-maze facilitates research on spatial learning and memory in bats. Its dual choice arms enable the investigation of various behavioral responses and can be customized to suit diverse research objectives. These arms are adaptable for holding odor cues, rewards, or incorporating wire mesh cages at their ends. Evaluation of light responsiveness is possible by inserting lamps or bulbs into the arms, and additional features like guillotine doors can be integrated as needed. Researchers can utilize the bat Y-maze to assess the impacts of diseases, brain lesions, and pharmacological interventions on learning and memory processes, ensuring straightforward data acquisition and analysis.
Trailing cues from prior trials can influence task performance in the bat Y-maze. Proper training of subjects is crucial for optimal task execution, relying on the subject’s innate exploratory motivation. Variables such as age, gender, and strain of the subjects can impact their task-related behaviors. Care must be taken to minimize unintended stimuli that could potentially affect the subject’s task performance.
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