Amphibian breeding programme contributes to reed frog conservation

  • 13 November 2013 | Carl Schloms – senior herpetologist | Category: Conservation

Pickersgill's froglets on a leaf

SAAMBR is committed to the conservation and preservation of amphibians, and to sharing our knowledge and passion for reptile and amphibian conservation with around 20 000 visitors every month – most of whom have an inherent fear of amphibians.

One such conservation project is our Pickersgill's reed frog (Hyperolius pickergilli) breeding programme. The tiny Pickersgill's reed frog – just 30mm long – is found on the east coast of Durban, South Africa and is threatened mainly due to the degradation of the coastal reed beds and coastal wetlands that form its natural habitat.

SAAMBR’s introduction to the Pickersgill's breeding programme began in September 2013 with a trip to Mt Moreland, north of Durban. My colleague Nick Evans and I wanted to establish whether the Pickersgill reed frogs had made their spring appearance.

Not only had they made an appearance, but an adult male H. pickersgilli was observed calling to a large female H. pickersgilli. We decided there and then to collect the courting pair in the hope that they would continue their breeding behaviour in our newly established breeding facility. We were keen to begin efforts to preserve this endangered amphibian after learning of its critically endangered status.

A macro shot of the developing embryos

We did not have to wait long, as 12 days later the pair produced an exceptionally large cluster of eggs. The egg mass was laid on the wall of the tub inhabited at the time by both the male and female. The egg cluster was coated in a clear gelatinous mass and it was apparent that weather played a significant role in the timing of her spawning, as it was noted that the day prior to her releasing the eggs, the ambient temperature was hot ahead of an approaching front.

An interesting observation was the apparent parental care shown by the female Pickersgilli. She was observed descending, then returning to the egg mass at regular intervals, seemingly keeping the egg mass moist. We decided to split the egg mass into three parts to allow us to test various incubation techniques. Two small sections of the eggs were delicately cut from the mass and placed in separate Petri dishes. The first Petri dish contained approximately 10 eggs and was filled with reverse osmosis water. The second Petri dish contained approximately 40 eggs and was placed on top of sterilised sphagnum moss before being filled with reverse osmosis water. The main egg mass was left undisturbed.

A misting system fitted with a timer was installed to lightly mist the egg mass on an hourly basis. The egg mass was monitored using a photographic macro lens to observe development. We observed free-swimming tadpoles in both Petri dishes four days after spawning. The main egg mass appeared to be sliding towards the water and the tadpoles were drawn by gravity to the lower half of the gelatinous mass.

The egg cluster coated in a gelatinous mass

It appeared that the mist stimulated the tadpoles emergence, albeit slowly, from the mass and into the water six days after being laid. This slow emergence continued at intervals throughout the day with the final tadpole count of 100 from this single main mass.

Success was achieved from all three methods and at the time of writing, we were the proud “parents” of 10 froglets, whose journey from egg to frog took 41 days.

From a scientific point of view, by observing the larger main mass of eggs we were able to make a few interesting observations that could affect the ex situ reproduction of H. pickersgilli:

  • As the egg mass appeared to depend on moisture in order to release the tadpoles, an absence of seasonal rainfall could affect an increase or decrease in population numbers
  • If what appeared to be parental care is confirmed by further study and observation, the tadpoles' survival is dependent on the wellbeing of their/a paren
  • Recorded duration between laying, free-swimming tadpoles and froglets which will add knowledge to similar organisations involved in the Pickersgill's project
  • Photographic microscopic records detailing growth and development of tadpoles

SAAMBR will continue to contribute to the conservation and preservation of amphibians, especially endangered and threatened species such as this tiny reed frog.

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