A man described feeling “the shudders” as more than 100 venomous red-bellied black snakes were removed from a pile of mulch in his Sydney backyard.

David Stein called Reptile Relocation Sydney last week after watching around six snakes slither into the mulch. He learned from an internet search that pregnant, known as gravid, red-belly blacks pile on top of each other before they give birth.

Reptile Relocation Sydney owner Cory Kerewaro said two of the captured adults gave birth to a total of 29 snakes in the bag while Cooper was still sifting through mulch catching more.

The final tally was five adults and 97 offspring caught, Kerewaro said.