Documentation

Introduction

The OSB (Oriented Strand Box) is used to study foraging behaviors in rodents. It is a rectangular box that is divided into two equal compartments in which food bait can be placed. The two-choice design of the box allows it to be easily adapted for different experimental protocols. It can utilize the basic decision-making protocol as the Y-Maze apparatus or be used in the assessment of anxiety-like behaviors. 

The foraging behaviors of rodents are affected by many environmental factors. Studies have observed that rodents make foraging and reproductive decisions based on predation risk, where they exhibit high levels of flight-related behaviors in the presence of predator odors (Hegab et al., 2014; Bramley, Waas, & Henderson, 2000).  The OSB Box can easily be used to observe the effect of predator odors on the decision-making behaviors of rodents. Food bowls are placed in each compartment of the OSB box, and the subjects are tasked to finish the bait from the two bowls. Predator odors can be attached to one of the food bowls to observe if the subjects demonstrate fear or anxiety-related behaviors. In contrast to other apparatuses that utilize unconditioned tests of anxiety such as the Light/Dark Box, the Elevated Plus Maze, and the Open Field Test, the OSB Box does not utilize an aversive stimulus. 

Other apparatuses used to observe foraging behaviors in rodents include the T-Maze, the Holeboard, and the Radial Arm Maze. 

Apparatus and Equipment

The OSB Box measures 74 x 37.5 cm in size with 40 cm long walls. The box is divided into two compartments (35 x 35 cm each) with each compartment containing an entrance (10 x 10 cm) on the same wall of the box. In the center of each compartment, a rubber bowl (13 cm in diameter and 1.5 cm high) is placed.

Training Protocol

Clean the box thoroughly before starting the trial. A tracking and recording system such as the Noldus Ethovision XT can be used to assist with observations.

The following is a sample protocol for the assessment of avoidance behaviors in rodents using the OSB Box:

Habituation and Pre-training

Bait the food bowls in the two compartments. Release the subject into the apparatus and allow it to eat all the bait from the two bowls. Conduct habituation sessions for 7 days. 

OSB Box task 

Bait the food bowls in the two compartments. Attach a piece of cardboard soaked in the test odor to the bottom of one of the bowls. Release the subject into the apparatus and allow it to eat all the bait from the two bowls. Alternate the test odor bowl between the two compartments as trials progress. Conduct trials for 3-5 consecutive days.

Literature Review

Investigation of the effect of predator scents on the foraging behaviors of wild rats

Stryjek, Mioduszewska, Spaltabaka-Gędek, and Juszczak (2018) tested whether wild Norway rats would avoid predator scents while foraging in a familiar habitat. The experiment was conducted using an OSB box that was placed in the middle of an indoor pen. Two black rubber bowls (control and experimental bowl) baited with 15 food pellets were placed in each of the two compartments. A piece of black cardboard soaked in predator scent was attached to the bottom of the experimental bowl, while black cardboard soaked in plain water was attached to the bottom of the control bowl.  

The predator scents consisted of urine samples of foxes, mountain lions (Puma concolor), dogs, cats, Sumatran tiger (Panthera tigris sumatrae), and coyotes (Canis latrans), as well as feces samples of African lions (Panthera leo), and TMT (2,5-dihydro-2,4,5-trimethylthiazoline) an anal gland secretion of foxes. The TMT sample was attached to the experimental bowl using 3 10 μl pipette tips fixed to the bowl using an odorless glue. The subjects were required to eat all 15 pellets from the two food bowls. After the experiment, three subjects were tested for Toxoplasma gondii, which could decrease the level of fear in the subjects. The results indicated that subjects did not display avoidance behaviors to any of the predator odors. No differences were observed in the time taken to eat the pellets between the experimental and control compartments. The total time taken to eat all the food pellets was 26 minutes and 12 seconds in the experimental sessions. The results for the Toxoplasma gondii tests were negative.

Data Analysis

The following can be observed using the OSB Box:

• Time taken to eat the first food pellet in the experimental compartment
• Time taken to eat the first food pellet in the control compartment
• Total time taken to eat all the food pellets in the experimental compartment
• Total time taken to eat all the food pellets in the control compartment
• Total time taken to eat all the food pellets from both compartments

Strengths and Limitations

Strengths 

The OSB Box can be used to observe foraging behaviors as well as anxiety-related behaviors in rodents. It can easily be adapted for different experimental protocols, such as the basic decision-making protocol used in the Y-Maze apparatus. Preferential behaviors to different visual stimuli can also be studied by using different colored food bowls. In contrast to the Light/Dark box that elicits stress and fear in the subjects, the OSB box does not utilize aversive stimuli. 

Limitations 

The exploratory behavior of the subjects is highly important in the performance of the task. Proper cleaning of the box is necessary to avoid the influence of odor cues from previous trials. The presence of unnecessary stimuli may affect the way the subject performs the task. Tasks may be influenced by age, gender, and strain of the subjects.

Summary

• The OSB Box is used to study foraging behaviors in rodents.

• It consists of a rectangular box that is divided into two choice compartments in which food bowls can be placed.

• The OSB Box can be used for different experimental protocols, such as in the observation of anxiety-related behaviors or preference behaviors to different visual cues or olfactory cues.

References

1. Bramley, G. N., Waas, J. R., & Henderson, H. V. (2000). Responses of wild Norway rats (Rattus norvegicus) to predator odors. Journal of Chemical Ecology, 26(3), 705-719. doi:10.1023/a:1005432322861 
2. Hegab, I. M., Jin, Y., Ye, M., Wang, A., Yin, B., Yang, S., & Wei, W. (2014). Defensive responses of Brandt’s voles (Lasiopodomys brandtii) to stored cat feces. Physiology & Behavior, 123, 193–199. doi:10.1016/j.physbeh.2013.10.030 
3. Stryjek, R., Mioduszewska, B., Spaltabaka-Gędek, E., & Juszczak, G. R. (2018). Wild Norway rats do not avoid predator scents when collecting food in a familiar habitat: a field study. Scientific reports, 8(1), 1-11. doi:10.1038/s41598-018-27054-4