The first ever proper count of seal pups born in the River Thames has spotted (*drumroll*)...138 baby seals!
Scientists from ZSL's (Zoological Society of London) said this provided clear evidence that harbour seals are breeding in the river that flows through southern England including London.
The big count took place in 2018 but the numbers are only being released now.
The total of 138 pups was tallied up after analysing hundreds of photos taken during the seals' summer pupping season.
The team took photos from a light aircraft as the seals rested, undisturbed on the sandbanks and creeks below.
It's much easier, and more accurate to count them this way, rather than chasing around after the constantly moving, playful creatures!
The Thames is home to both harbour seals and grey seals, though it is only the harbour seals that breed there.
Project Manager, Anna Cucknell, who leads ZSL's Thames conservation explained: "Incredibly, harbour seal pups can swim within hours of birth which means they are well adapted to grow up in tidal estuaries, like the Thames. By the time the tide comes in they can swim away on it.
"Grey seals, on the other hand, take longer to be comfortable in the water, so breed elsewhere and come to the Thames later to feed."
The river is also home to many animals including more than 100 species of fish, including two species of shark, short-snouted seahorses and the Critically Endangered European eel.
Conservation Biologist, Thea Cox said: "The seals would not be able to pup here at all without a reliable food source, so this demonstrates that the Thames ecosystem is thriving and shows just how far we have come since the river was declared biologically dead in the 1950s."
ZSL has conducted Thames seal population counts every year since 2013. The most recent results, from 2017, recorded 1,104 harbour seals and 2,406 grey seals across the estuary.
This shows that seal numbers in the Thames are rising, but it is not yet known whether this is due to resident seals having pups or from adults migrating - or coming - from other regions where colonies are known to be getting smaller.
For the first time in 2018, the team at ZSL undertook a breeding survey. It's hoped that by using the two sets of surveys together in the future, this will allow researchers to better understand the seals in the Thames and the reasons behind their changing numbers.