Behaviour of the Pleistocene marsupial lion deduced from claw marks in a southwestern Australian cave

Abstract

The marsupial lion, Thylacoleo carnifex, was the largest-ever marsupial carnivore, and is one of the most iconic extinct Australian vertebrates. With a highly-specialised dentition, powerful forelimbs and a robust build, its overall morphology is not approached by any other mammal. However, despite >150 years of attention, fundamental aspects of its biology remain unresolved. Here we analyse an assemblage of claw marks preserved on surfaces in a cave and deduce that they were generated by marsupial lions. The distribution and skewed size range of claw marks within the cave elucidate two key aspects of marsupial lion biology: they were excellent climbers and reared young in caves. Scrutiny of >10,000 co-located Pleistocene bones reveals few if any marsupial lion tooth marks, which dovetails with the morphology-based interpretation of the species as a flesh specialist.

Figure 1. Location and map of Tight Entrance Cave.

(a) Australia with arrow indicating position of locality. (b) Leeuwin–Naturaliste Region showing mean annual rainfall isohyets (mm) and caves containing palaeontological deposits preserving remains of Thylacoleo carnifex. (c) Plan view of main chamber showing focus areas for claw-mark documentation, excavation area and topography relative to sea level. (d) Cross section of central rock pile (CRP). The current entrance opened in 1976. The hypothesised former (Pleistocene) entrance in the main chamber ceiling is now blocked. Map generated in ArcMap10.1 using the CrossView extension; data collected on a Sokkia 3030R Total Station.

Figure 2. Examples of claw-marked areas in Tight Entrance Cave.

(a) Cave wall south. (b) Central rock pile west. (c) Central rock pile south sub-region 2. (d) Boulder sub-region 2. (e) Boulder sub-region 8. Scale bars = 10 cm.

Figure 3. Histogram of inter-digital spacing for the Tight Entrance Cave scratch sets.

Lines above represent the ranges exhibited by the taxa considered in the comparative study, with vertical lines representing means. Arrow on Thylacoleo carnifex indicates that this extends beyond the range of the histogram. Silhouettes not to scale. Sourced from Phylopic.org, all under public domain except: Sarcophilus (http://phylopic.org/image/58cc56c2-5a36-4031-be9f-28c86f77963c/) by Sarah Werning; Thylacinus (http://phylopic.org/image/bacd7beb-7b6f-4466-a31a-715509b9532f/) by Michael Ströck; and Petrogale (http://phylopic.org/image/eccfc4b3-faee-4384-b35b-64c788f30846/) by T. Michael Keesey, all unchanged under Creative Commons Attribution-ShareAlike 3.0 Unported licence. The license terms can be found at: https://creativecommons.org/licenses/by-sa/3.0/.

Figure 4. Histogram of bone modification types from Tight Entrance Cave indicating confidence with which marks were attributed to biological agents (Reliability index).

Percentage refers to that of all bones inspected for taphonomic damage (10,621).