Pellis, Sergio

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https://opus.uleth.ca/handle/10133/5256

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Browsing Pellis, Sergio by Subject "Animals--Play behavior"

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    The development of juvenile-typical patterns of play fighting in juvenile rats does not depend on peer-peer play experience in the peri-weaning period
    (eScholarship Publishing, University of California, 2015) Himmler, Brett T.; Himmler, Stephanie M.; Stryjek, Rafal; Modlinska, Klaudia; Pisula, Wojciech; Pellis, Sergio M.
    Play fighting in rats involves attack and defense of the nape. To protect the nape, rats use a variety of defensive tactics, with different strains having specific preferences. Targeting of the nape is established before weaning and defense matures over the course of the week preceding and the week proceeding weaning. Thus, it is possible that experience from engaging in immature forms of play is needed to consolidate the nape as the playful target and for the development of the juvenile-typical pattern of defense. Two experiments were conducted to evaluate this possibility. For the first experiment, male rats were reared over the week post-weaning in either pairs or alone, and their play tested with unfamiliar partners when juveniles (31-34 days). For the second experiment, during the week preceding weaning, male and female rats were placed into one of three conditions: (1) with the mother and no peers, (2) with same-sex siblings but no mother, or (3) with both the mother and same-sex siblings. The subjects were tested in same-sex, samecondition pairs when juveniles (31-34 days). Rats from all conditions, in both experiments, attacked the nape during play fighting and developed the same juvenile-typical patterns of playful defense. This suggests that the experience of peer-peer play in the peri-weaning period is not necessary for the development of the attack and defense components of juvenile-typical play.
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    The development of strain typical defensive patterns in the play fighting of laboratory rats
    (eScholarship Publishing, University of California, 2014) Himmler, Stephanie M.; Lewis, Jena M.; Pellis, Sergio M.
    During play fighting, rats attack and defend the nape, which if contacted is nuzzled with the snout. While all strains of rats use the same suite of defensive tactics to protect the nape, different strains use some tactics more frequently. This study tests two hypotheses for this strain difference: (1) each strain has a preference for using particular tactics and (2) strain differences in defense are a byproduct of strain differences in patterns of nape attack. Juvenile Long-Evans (LE) and Sprague-Dawley (SD) males, raised in same strain quads from shortly after weaning to the early juvenile period (i.e., 24-31 days), were tested with unfamiliar same-strain and different-strain partners (Experiment 1) and LE and SD males raised in mixed LE-SD quads were tested with both familiar (Experiment 2) and unfamiliar same-strain and different-strain partners. If hypothesis (1) were true, they would maintain strain-typical defense patterns irrespective of the strain of the attacking partner, whereas if hypothesis (2) were true, it would vary with the strain of the attacking partner. Hypothesis (1) was supported in the first experiment; all the rats maintained their strain-typical patterns regardless of the partner’s strain. However, Experiments 2 and 3 supported neither hypothesis, as each animal displayed strain-divergent behavior when playing with partners of either strain. Given that in Experiments 2 and 3, subjects were reared in mixed-strain groups, it is possible that, during the early juvenile period, play fighting experiences shape strain-typical patterns of use of defensive tactics.
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    Pinning in the play fighting of rats: a comparative perspective with methodological recommendations
    (eScholarship Publishing, University of California, 2016) Himmler, Stephanie M.; Himmler, Brett T.; Stryjek, Rafal; Modlinska, Klaudia; Pisula, Wojciech; Pellis, Sergio M.
    During play fighting, rats attack and defend the nape of the neck and during the course of this competitive interaction, they may adopt a configuration in which one animal stands over its supine partner (i.e., pin). Because the pin configuration is typically frequent and relatively easy to identify, it has been widely used as a marker to detect the effects of experimental treatments. In the present study, the frequency of pinning during standardized, 10-min trials in three strains of rats, Long Evans hooded (LE), Sprague-Dawley (SD) and wild (WWCPS), was compared. LE and SD had higher rates than WWCPS rats (#/min: 6.5, 5.5, 1.5, respectively). When adjusted for strain differences in the frequency of attacks, SD as well as WWCPS rats had lower rates of pinning compared to LE rats. Both SD and WWCPS rats were less likely to use tactics of defense that promote pinning. Moreover, while the majority of the pins achieved in LE rats arose from the defender actively rolling over onto its back, the majority of pins in WWCPS rats arose because one partner pushed the other onto its back. SD rats were intermediate in this regard. Finally, once they do adopt the pin configuration, SD rats are less likely to remain supine than LE and WWCPS rats. That is, both SD and WWCPS rats have significantly fewer pins than LE rats, but a different combination of factors account for this. These data highlight the need to use a battery of measures for ascertaining the effects of experimental manipulations on play. Some suggested guidelines are provided.