Pack or Loner?

 It is unclear exactly how most dinosaurs hunted prey. We have hypotheses, some more well supported and considered than others, but unfortunately we do not have any trail cameras or candid videos documenting behaviors of dinosaur hunting. As many of us may have heard, at least once in our lifetime, many dromaeosaurs are thought to have been pack hunters; tracking, ambushing, and taking down prey that was far larger than a single animal to feed a large group of predators. Not all of the species within this group of animals is thought to have exhibited this complex social system. Often, wolves are used in analogy to describe these pack hunting behaviors, and for good reason. Utahraptor, as the largest of the dromaeosaurs, is one of those dinosaurs thought to have hunted this way and is often compared to wolves. Recently Frederickson et al. (2020) analyzed the teeth of Deinonychus and concluded that pack hunting was not likely to have been a characteristic social interaction in these smaller dromaeosaurs, but no such study has been conducted with Utahraptor. For the moment at least the idea of Utahraptor as a pack hunter still exists. This behavior was central to the theme of the novel discussed the other day. Additionally, this behavior is hinted at by a number of studies of Utahraptor including one that looks at a hypothesized quicksand death trap that may have enveloped an entire pack including juvenile animals (Kirkland et al. 2016). It is possible that, in addition to a complex social system wherein pack mentalities developed, that Utahraptor may have been simply too large to chase fast prey and too small to take on large prey alone. The describing paper, Kirkland et al. (2001), concluded that Utahraptor was likely slower than its cousins Velociraptor and Deinonychus. 

Rather than post an image directly in here today, I refer you to Julius Csotonyi's interpretation of the quicksand event that may have led to the discovery of a pack of fossilized Utahraptors as described in Kirkland et al. (2016).

Literature Cited

Frederickson, J. A.; Engel, M. H.; Cifelli, R. L. (2020). "Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis". Palaeogeography, Palaeoclimatology, Palaeoecology: 109780. doi:10.1016/j.palaeo.2020.109780

Kirkland, J.I.; Simpson, E.L.; DeBlieux, D.D.; Madsen, S.K.; Bogner, E.; Tibert, N.E. (2016). "Depositional constraints on the Lower Cretaceous stikes quarry dinosaur site: Upper yellow cat member, cedar mountain formation, Utah". PALAIOS. 31 (9): 421–439. doi:10.2110/palo.2016.041