Today, the red kangaroo is the biggest living hopping animal and weighs around 90 kg.

Throughout the Ice Age, some kangaroos grew more than two times the size of that– some reaching up to 250 kg.

For several years, scientists thought these giants should have deserted hopping, as earlier research studies recommended that hopping would end up being mechanically difficult above about 150 kg.

“Previous quotes were based upon just scaling up contemporary kangaroos, which might suggest we miss out on essential physiological distinctions,” stated Dr. Megan Jones, a postgraduate scientist at the University of Manchester and the University of Melbourne.

“Our findings reveal that these animals weren’t simply bigger variations these days’s kangaroos, they were developed in a different way, in manner ins which assisted them handle their massive size.”

In the brand-new research study, Dr. Jones and her associates studied the hindlimbs of 94 modern-day and 40 fossil specimens from 63 kangaroo and wallaby types, consisting of members of the extinct huge kangaroo group Protemnodonwhich lived throughout the Pleistocene date, in between 2.6 million and 11,700 years earlier.

For each types they utilized released quotes of their weight and the length and size of their 4th metatarsals– an extended foot bone secret for hopping in contemporary kangaroos– to determine whether they might have endured the stress of hopping.

The researchers then compared the heel bone structures of huge kangaroos with those of modern-day kangaroo types.

They approximated the size of the tendon needed to stand up to the forces needed to help with hopping in huge kangaroos and determined whether their heel bones would have been big enough to accommodate tendons of this size.

The authors forecast that the metatarsals of all huge kangaroo types would have been robust enough to stand up to the physical tension brought on by hopping, which their heel bones would have been huge enough to enable the tendon width needed for hopping.

Together, the findings recommend that the hindlimbs of all huge kangaroos were robust enough for them to be able to hop.

The scientists propose that it is not likely huge kangaroos would have relied on hopping for all mobility owing to their big body sizes making this ineffective over longer ranges.

They keep in mind that erratic hopping is currently seen in much of today’s smaller sized types, such as hopping rodents and smaller sized marsupials.

They hypothesize that brief, fast bursts of hopping might have assisted some huge kangaroo types avert predators, such as those coming from a group of extinct marsupial lions called Thylacoleo

“Thicker tendons are much safer, however they keep less flexible energy,” stated Dr. Katrina Jones, a scientist at the University of Bristol.

“This most likely made huge kangaroos slower and less effective hoppers, much better matched to brief bursts of motion instead of long-distance travel.”

“But hopping does not need to be very energy effective to be helpful, these animals most likely utilized their hopping capability to cross rough ground rapidly or to get away threat.”

“Our findings add to the idea that kangaroos had a more comprehensive environmental variety in ancient Australia than we discover today, with some big types grazers like modern-day kangaroos while others were web browsers– an environmental specific niche not seen in today’s big kangaroos,” stated Dr. Robert Nudds, a scientist at the University of Manchester.

The outcomes appear in the journal Scientific Reports

_____

M.E. Jones et al2026. Biomechanical limitations of hopping in the hindlimbs of huge extinct kangaroos. Sci Rep 16, 1309; doi: 10.1038/ s41598-025-29939-7