Threat status 

2017 NZ Conservation Status: At Risk – Declining 

2015 IUCN Red list of Threatened Species: Least concern

Description 

The nocturnal Hochstetter’s frog (Leiopelma hochstetteri) was the first native species of frog discovered by Europeans in New Zealand during the gold rush in the Coromandel. Hochstetter’s frogs are distinct from our two other native frog species and are the most commonly encountered.

^{Image by ©Oscar Thomas}

Habitat

Hochstetter’s frogs are the only semi-aquatic (lives on land and in the water) of the native species. They are nocturnal and shelter by day in wet crevices or under stones or logs close to the water’s edge in shaded streams. They are the most widely distributed living species of native frog with at least 13 genetically distinct, fragmented and isolated populations across the northern half of the North Island. In some areas, Hochstetter’s frog occurs sympatrically (together) with Archey’s frog (Leiopelma archeyi).

Breeding 

Hochstetter’s frog is an aquatic breeder, laying small egg strings between 9-20 eggs. Hochstetter’s frog does not display parental care and they have a tadpole-like larvae stage where the embryos swim, but do not feed, after hatching. Eggs are laid in wet seepages close to the stream, and male frogs do not guard them.

Threats

Introduced Predators 

Introduced mammalian predators are a significant threat to all New Zealand native frogs. Increasingly feral pigs are thought to be severely impacting Hochstetter’s frog populations in the coromandel as pig rooting destroys habitat, during which they may incidentally be consumed or squished. It is currently unknown whether wild pigs predate on Hochstetter’s frog or accidentally ingest them when looking for food on along stream margins. 

Rats and mice are also believed to be impacting Hochstetter’s frogs. Populations have benefited from predator control efforts in the past. But increased mice numbers after rat control efforts have caused increased juvenile mortality.

Disease

As for all native frogs, chytrid fungus likely poses a low risk to Hochstetter’s frog populations. Chytrid fungus has never been detected in wild Hochstetter’s populations, despite the disease circulating widely in other native and introduced frogs. It is thought Hochstetter’s frogs may be naturally immune to the chytrid fungus. Experimental infection in the lab caused no clinical symptoms and all frogs tested negative for chytrid fungus after 10 weeks.  

Habitat Disturbance

Habitat disturbance is a primary and ongoing concern for Hochstetter’s frog. Currently habitat disturbance occurs both directly (e.g. deforestation, gold mining, storm water discharge) or indirectly (e.g. feral goats and pigs causing erosion leading to silt entering streams). Hochstetter’s frogs have been found in exotic pine plantations which often destroys stream health through excessive sedimentation, limiting egg survival. The harvesting of trees occurs every 20-30 years, and likely significantly reduces Hochstetter’s frog population numbers. 

^{Image by AJ Beauchamp}

^{Image by ©Oscar Thomas}

^{Image by ©Oscar Thomas}

Captive Populations

There is a captive population of Hochstetter’s frogs located at Hamilton Zoo, who are working hard to perfect a captive breeding programme.