Dinosaurs may have been 'super spreaders', NZ study finds

The optimum seed spreader might have been a dinosaur such as triceratops, which may have weighed eight to 10 tonnes and moved at a maximum speed of around 25 km/h. Photo / 123RF

Move over kererū: a new Kiwi study has suggested another, much heftier, animal likely played a big part in helping plants to spread - dinosaurs.

The research, by the University of Auckland's Professor George Perry during last year's Covid-19 lockdown, has suggested some of the prehistoric giants might have been able to spread seeds as far as 30km.

Seed dispersal is critical for helping forests survive - seeds of most New Zealand native trees are mainly spread by birds like kererū and tūī - and Perry's new study offers a new insight into ecosystems that existed some 65 million years ago.

Evidence previously gained from fossils has indicated that seeds consumed by dinosaurs can remain intact in their stomachs, suggesting a possible role in helping plants to spread in the ancient world.

That led Perry to look at how far dinosaurs may have spread the seeds, by modelling the animals' likely travel speeds along with their likely frequency of defecation – factors that can be estimated from body weight.

His work suggested that an optimum seed spreader might have been a dinosaur such as triceratops, which may have weighed eight to 10 tonnes and moved at a maximum speed of around 25km/h.

Another dinosaur of similar body mass and potential seed dispersal capacity was stegosaurus, which may have weighed six to eight tonnes.

These dinosaurs may have spread seeds on average as far as 4-5km and in rare cases more than 30km.

To Perry, the work pointed to the complex relationships of living things within ecosystems – a topic especially relevant as the world experienced what some scientists describe as the "sixth mass extinction".

"When we think about extinct animals, it's easy to just think of a long list – but in fact they all played inter-linked roles in our ecosystems."

His study, just published in the journal Biology Letters, drew on his ongoing and unpublished research with colleagues at Manaaki Whenua-Landcare Research into the roles that extinct New Zealand birds may have played in dispersing seeds.

It also added to previous speculation on the role that dinosaurs may have played in spreading plants.

Fossilised plants with features that suggest they may have been dispersed by animals date as far back as 280 million years – and seeds from fossilised gut contents are just as old.

Dinosaurs went extinct about 65 million years ago, when a meteorite slammed into the Earth.

Still, understanding exactly what role dinosaurs played in helping plants to spread may be difficult or impossible to establish from the fossil record.

Although dinosaurs certainly moved seeds, scientists don't know anything about the germination of those seeds.

At the time dinosaurs roamed the planet, New Zealand was covered in lush rainforest and was a much larger land area than today – almost half the size of Australia.

It was also almost certainly home to one of the largest dinosaurs known to exist - the titanosaurid - which reached up to 45m in length, and weighed up to 50 tonnes.