Hunting for insight: an analysis of hunting behaviors in mice

Behaviors revolving around the acquisition of food resources are complex and crucial processes for many organisms. Hunting is an especially interesting behavior, which involves complex cognitive and social behaviors. In order to study rudimentary hunting behaviors in a controlled setting a model organism that is apt for laboratory work, is required. Up until now, there has not been an organism in which one could feasibly study hunting behaviors. The Gregg lab has recently discovered that laboratory mice have the innate capacity and drive to hunt crickets. This cognizance incited our study of hunting behaviors in mice.

Hunting for Insight: An analysis of hunting behaviors in mice University of Utah Department of Neurobiology and Anatomy Natalie Meadows Dr. Christopher Gregg Introduction Specific Aims Methods Results Conclusion References Behaviors revolving around the acquisition of food resources are complex and crucial processes for many organisms. Hunting is an especially interesting behavior, which involves complex cognitive and social behaviors. In order to study rudimentary hunting behaviors in a controlled setting a model organism that is apt for lab-oratory work, is required. Up until now, there has not been an organism in which one could feasibly study hunting be-haviors. The Gregg lab has recently discovered that labo-ratory mice have the innate capacity and drive to hunt crickets. This cognizance incited our study of hunting be-haviors in mice. One of the principal research areas for the Gregg Lab is the molecular pathways that influence motivated behav-iors. Motivational states can strongly influence and direct various behaviors. There are many types of motivated be-haviors, many of which have been extensively investigated in the literature. Behaviors may be motivated by positive means, such as the promise of a reward. Likewise, behav-iors may be negatively motivated and are carried out in order to avoid an undesirable consequence. Consummato-ry behaviors are positively motivated behaviors, which are behaviors that are positively driven by both caloric and emotional needs (1). The neurobiological processes that influence the motivational behavior states involved in food acquisition and consumption are critical to organism sur-vival, and significantly influence the normative behavior, and morphology of the organism. The Gregg lab has engaged in a variety of studies aimed at better understanding of feeding and foraging behaviors, and the neural mechanisms influencing these behaviors. These studies have revealed interesting and novel insights into the behaviors and motivation that influence feeding and foraging such as exploratory behaviors, motivation to feed, and search strategies. Hunting is a very interesting, and relatively understudied, food-oriented behavior. Hunting behaviors involve the pur-suit, capture, and consumption of a prey item. The neuro-behavioral processes involved in eliciting hunting-type be-haviors are also unknown. Single Cricket Solitary Hunting Assay Group Hunting Assay Multiple Cricket Solitary Hunting Assay The primary assay was developed to test the hypothesis that there would be variance in hunting behaviors be-tween mice that had been fasted over-night (18-20 hours), and non-fasted mice. I developed an assay in which a single mouse was placed in an empty square arena, and allowed to adjust to the arena for 10 minutes, after-which 5 crickets are place in the arena and micehunt for 30 minutes. A total of 12 mice were tested; once It was also of interest to do separate analyses of group and solitary hunting behaviors. For these assays, a simi-lar methodology as was used in the multiple cricket soli-tary hunting assay. For solitary trials, mice were fasted for a period of 6-8 hours prior to testing. One mouse is placed in the arena per trial, and allowed to adjust to the novel environment for a short duration of time (10 minutes), after which one cricket is placed into the arena. Mice were tested for a period of 30 minutes in which many of them would hunt and kill the cricket. A total of 12 mice were tested, and each mouse was tested 3 times, yielding a total of 36 solitary behavior trials. All trials were video-recorded and scored at a later time. To study and understand group behavior, I developed an assay in which three mice were tested per trial. Mice were fasted 6-8 hours before testing. In the group assay three mice were placed together in the arena, and allowed to adjust to the arena for 10 minutes. After this time three crickets were placed into the arena with the mice, allowing for a 1:1 ratio of mouse:cricket. Mice were video-recorded for a period of 30 minutes in order to observe and gather data about group hunting behavior. A multitude of interest-ing group behaviors emerged during this study. Mice fre-quently exhibit stealing behaviors, taking a cricket from the mouse that did the killing. In conjunction with this stealing behavior mice have also displayed ‘defense of the kill' be-haviors in which mice ward off potential thieves, and hold on to their respective kill. All trials were video-recorded and scored at a later time. From the multiple cricket solitary hunt assay we found that both fasted and non-fasted mice ex-hibit the innate im-pulse to kill and con-sume crickets, re-gardless of their level of hunger. A.) Mice kill the same number of crickets in both fasted and non-fasted states. (t-test, n=12). B.) Non-fasted mice consume nearly the same percent-age of kills as fasted mice, although fasted mice overall consume a greater percentage than non-fasted mice. (t-test, n=12) Number of Kills Number of Crickets Killed Fasted Non-Fasted 0 1 2 3 4 5 Percent Kills Consumed Proportion of Crickets Eaten / Total Fasted Non-Fasted 0.0 0.5 1.0 n=12 1.5 n=12 A B Multiple Cricket Solitary Hunting Latency To First Kill Latency To First Kill (sec) Fasted NonFasted 0 100 200 300 Latency To First Strike Latency to First Strike (sec) Fasted NonFasted 0 50 100 150 200 *** *** (p < 0.0001) (p < 0.0001) C D Multiple Cricket Solitary Hunting Latency measures were taken, measur-ing the amount of time preceding be-haviors such as making an initial attack on a cricket (first strike) and kill-ing the first cricket. Latency measures have been widely used as indicators of motivation to perform a behavior, or to achieve a desired result. These mea-sures demonstrated significant variance in the behavioral mo-tivation state of fasted mice vs. non-fasted mice in carrying out cricket hunting behaviors. C.) Fasted mice make their first kill in a shorter mean time when compared to non-fasted mice. (t-test, n=12). D.) The mean time it takes fasted mice to make first strike on crickets is significantly less than the mean time for non-fasted mice. (t-test, n=12) The group assay revealed many complex social behaviors, such as stealing and ‘defense of the kill' behaviors. It was noted that mice display hierarchical hunting strategies; meaning mice that are more inclined to kill crickets are less inclined to steal crickets from other mice. Many behaviors of interest were scored from the solitary hunting trials. These include: latency to strike, duration of pur-suit for prey, latency to kill, and time spent with kill post-cap-ture. It is of interest to our study to do a comparative analysis using the scorings from the preliminary solitary hunting trials, with those of future trials comparing additional mouse strains, males and females, and various age groups. A number of hunting behaviors evoke an array of complex cognitive and social behaviors. Because human behavior is often characterized by advanced cognitive abilities and en-hanced sociality, a multitude of hypotheses have emerged that assert that activity of hunting had important implications in human evolution. Several of these hypotheses are directed at increasing our understanding of various neuropsychiatric disor-ders by utilizing an evolutionary framework. It has been proposed that some genes associated with cer-tain neuropsychiatric disorders such as ADD/ADHD and autism may have been positively selected for in humans, due to the fit-ness benefits achieved by individual's manifesting such behav-iors (3,4). Characteristic behaviors of these diseases may have provided individuals with a competitive advantage for food pro-curement in ancestral times. For these reasons we plan to test transgenic disease model mice in our hunting assays. We anticipate using mice featuring a single nucleotide (G406R) mutation, in conjunction with an inverted neomycin cassette in exon 8A (TS2-neo) in the CACNA1C gene, which codes for a L-type CaV1.2 calcium channel (2). Mutations in the CACNA1C gene have been shown to be correlated with several neuropsy-chiatric diseases; primarily Timothy Syndrome, as well as autism spectrum disorder, bipolar disorder and schizophrenia (5). We anticipate testing the TS2-neo mice adult mice through the hunting the hunting behavioral assay, in order to better un-derstand and test the potential implications ASD-like charac-teristics may have for hunting and feeding behaviors. 1.) Barson J, Morganstern I. Leibowitz SF. (2012). Neurobiology of con summatory behavior: Mechanisms underlying overeating and drug use. ILAR J, 53(1). Retrieved from http://www.nc bi.nlm.nih.gov/ pubmed/23520598 2.) Bader PL. et al. Mouse model of Timothy syndrome recapitulates triad of autistic traits. (2011). Proc Natl Acad Sci USA, 108(37). 3.) Moyzis R., et al. Evidence of positive selection acting at the human dopamine receptor D4 gene locus. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.012464099 4.) Reser, E. (2011). Conceptualizing the autism spectrum in terms of natural selection and behavioral ecology: The solitary forager hypothesis. Evolutionary Psychology, 9(2): 207-238. Retrieved from http://www.epjournal .net/wp-content /uploads/EP09207 238.pdf 5.) Thimm, Kircher T. et al (2011). Effects of a CACNA1C genotype on attention networks in healthy individuals. Psychological Medi cine, 41. doi: 10.1017/S0033291710002217 Group Hunting Assay Fasted and non-fasted mice kill and consume similar numbers of crickets Acknowledgments I want to sincerely thank the members of the Gregg Lab: Chris, Tina, Elliot, Coni, Wei-cho, and Paul for their continuous assistance and sup-port. I would also like to thank Rosemary Gray and Lori Stutz for their incredible dedication to the Bioscience Undergraduate Research Pro-gram. I am very grateful to the Neuroscience Undergraduate Research Program (NURP) for providing the funding for my research. Thank you all. Hunting assay with one mouse and ve crickets Mouse in pursuit Mouse dining on cricket Multiple mice hunting One mouse attempting to steal from another Fasted mice strike and kill first cricket in less time than non-fasted mice in a fasted state, and once in a non-fasted state, for a total of 12 fasted trials, and 12 non-fasted trials. All trials were video-recorded and scored at a later time.