Journal of the Royal Society of Western Australia, 86:115-116, 2003 
Surface activity of arid- 
Q° tes adapted frogs 
- G G Thompson 1 , S A Thompson 1 
& J L Fraser 2 
’Centre for Ecosystem Management, Edith Cowan 
University, Joondalup Dr, Joondalup WA 6027 
E g.thompson@ecu.edu.au E s.thompson@ecu.edu.au 
2 School of Animal Biology, University of Western Australia, 
Crawley WA 6009 E mulgara@cyllene.uwa.edu.au 
(Manuscript received March 2003; accepted April 2003) 
Abstract. The arid-adapted Neobatrachus sutor and 
Pseudophryne occidentalis are most surface active 
immediately after heavy rain. The number of these frogs 
caught in pit-traps declined rapidly over a four day 
period after rain ceased. As we found no evidence of 
breeding, we concluded that N. sutor had come to the 
surface to feed, most probably on termites which we 
observed in very large numbers. We estimate the number 
of occasions that these two species of frogs could have 
been surface active, based on rainfall data, to be > 9 and 
> 17 yr* 1 respectively. 
Key words: Neobatrachus sutor , Pseudophryne occidentalis , 
frogs, abundance, activity 
Introduction 
Arid-adapted frogs spend most of their lives buried 
underground waiting for rain (Morton et al. 1993; Predavec 
& Dickman 1993; Read 1999). Some form cocoons ( e.g. 
Neobatrachus sutor ; Withers 1995) and others find a moist 
location under rocks or vegetation to minimise water loss 
and survive for extended periods (e.g. Pseudophryne 
occidentalis; Tyler 1994). These frogs surface immediately 
after heavy rain. Read (1999) reported that surface activity 
of Neobatrachus centralis in the chenopod shrubland around 
Olympic Dam was not restricted to rainfall events, but 
they were mostly found surface active after more than 5 
mm of rain; N. centralis was active for up to 20 days after 
heavy rain, and disappeared just before the ponds dried 
out. Morton el al. (1993) reported that arid-adapted frogs 
(Neobatrachus spp, Notaden nichollsi, Uperoleia micromeles 
and Cycloram maini ) were most abundant immediately 
after heavy rains and their numbers 'tailed off within 
about two days of the cessation of showers. They 
suggested that arid-adapted frogs do not always attempt 
to breed when they emerge, coming to the surface to feed 
and replenish energy stores in preparation for a further 
period of inactivity. 
We report here on activity periods for N. sutor and P. 
occidentalis immediately after two rainfall events at Ora 
Banda (30° 22'S, 121° 03'E; Eastern Goldfields region) 
during January/February 2003. 
Materials and methods 
We surveyed small terrestrial fauna at four sites in the 
Ora Banda area. Frogs were captured in either 20 L PVC 
bucket pit-traps or 150 mm PVC stormwater pipes. Forty- 
eight pit-fall traps were arranged in eight rows of six pit- 
© Royal Society of Western Australia 2003 
traps (alternating bucket and pipe) in the undisturbed 
areas. We also had 36 pit-traps in six rows of six on the 
sides and 36 pit-traps in six rows of six on the top of the 
mining waste dumps. A fly-wire drift fence joined each 
line of six pit traps. All pit-traps were open on the nights 
of 28 January to 4 February 2003. The Paddington gold 
mine (within 25 km of all sites) recorded 6 mm of rain on 
27 January, 15 mm on 28 January, 9 mm on 2 February 
and 2.5 mm on 3 February. Summer thunderstorms are 
often very localised and rainfall can vary appreciable 
over a few kilometres as it did on these two occasions. 
Puddles and pools of water were evident along the 
roadside for two days after each rainfall event. Other 
than where runoff accumulated near the base of mining 
waste dumps, we found no substantial pools of water in 
areas not disturbed by mining activity two days after 
rain ceased. However, water along roadsides remained 
for a longer period. Night searches for frogs were 
undertaken on l sl and 2 nd February at all four sites. 
Results 
Seventy six N. sutor and 288 P. occidentalis were 
captured during the seven nights of trapping. We found 
a few P. occidentalis in some of the larger ponds on the 
top of a waste dump during the day. Both species of 
frogs were most abundant the first night after heavy rain 
and the number pit-trapped rapidly declined to very low 
levels by three to four days after the rain ceased (Fig 1). 
Having driven approximately 60 km around the study 
sites at night we heard only one N. sutor calling from a 
pond and a large number of P. occidentalis calling from a 
variety of locations. We saw no tadpoles in residual 
ponds after the rain, but the water was very coloured 
and visibility was very poor, so if tadpoles were in the 
ponds they may not have been seen. We did not search 
for P. occidentalis eggs in moist tunnels. 
A large number of termite alates were observed 
during the build up to the first thunderstorm and on the 
night it first rained. We observed many swarms of 
termites active on the surface of logs and the leaf litter 
mid-morning on the first day after heavy rain. 
Discussion 
Arid-adapted frogs come to the surface after heavy 
rain for two purposes, to breed and to restore energy 
reserves. Presumably, if there is insufficient rain to 
enable frogs to successfully breed then they feed and 
again go to ground waiting for more suitable conditions. 
Figure 1. Number of N. sutor and P. occidentalis caught in pit- 
traps after rainfall. 
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