80
A. R. MAIN
On the other hand the ponds on mndy Roil are fed for a considerable
period by seepage from the surrounding low sand hills. These two
observations suggest that selection against a prolonged breeding 88&Bon
must be very intense in the “clay” race as the offspring from all late
breeding animals would fail to metamorphose. On the other hand, in
the “sacd” race, selection must be strong for a prolonged breeding
season because water will not persist long enough for larval develop-.
ment to be completed unless the sand is fully saturated. Examples
occurred in 1954 and 1959, following heavy early winter rains, when
ponds on sandy soil filled for a few weeks and then dried out to fill
again later in the winter. In both these years early breeding failed to
lead to recruitment. However, while ponds on clay soil filled from the
same early rains, they did not dry until larvas had metamorphosed.
H. POPULATION SIZE
Most frog apecies are not amenable to study at the population level
because populations are not discrete. All burrowing frogs and many
others can only be caught in large numbers when they are breeding and
those which have only a short breeding period give no opportunity for
estimates of population size by using a technique of mark and recapture.
However, in a discrete population of the burrowing frogs Hebioporus
eyrei which remained adjacent to the breeding sites at Lighthouse
Swamp. Rottnest Island, Lee (1967) studied marked animals outside
the breeding season. He estimated the population to comprise 202 adult
males (limits 110-294) and 78 adult females (limits 71-85) on 24 November 1956. Juveniles were not sampled at this time but at the same date
in 1955 these were estimated to number 2241.
An estimate of population size waa attempted on a small breeding
congress of Neobatrmhw pelobatoides at Attadale during 1981. Prior to
30 June 1961, no water was present, no breeding had taken place and
Neobatrmhw could not be found. On the night of 30 June, 16 males
and 2 females of N . p e b b a t o i k were individually marked by toe clipping. Over the nighta of 1, 2 and 3 July, breeding continued and a total
of 75 males and 10 females were marked. On the night of 4 July there
was no breeding and neither males nor females could be found in the
vicinity. No female waa recaptured. The population estimate based on
the males recaptured on the fourth night waa 116 (Main, unpublished).
An attempt to follow the success of this breeding was frustrated when
the are(, was developed as a housing estate before recruitment oould be
measured. In subsequent years it has proved impossible to find a similar
discrete population of this specie8 on which to m w u r e reproductive
success aqd longevity.
A. R. MAIN
On the other hand the ponds on mndy Roil are fed for a considerable
period by seepage from the surrounding low sand hills. These two
observations suggest that selection against a prolonged breeding 88&Bon
must be very intense in the “clay” race as the offspring from all late
breeding animals would fail to metamorphose. On the other hand, in
the “sacd” race, selection must be strong for a prolonged breeding
season because water will not persist long enough for larval develop-.
ment to be completed unless the sand is fully saturated. Examples
occurred in 1954 and 1959, following heavy early winter rains, when
ponds on sandy soil filled for a few weeks and then dried out to fill
again later in the winter. In both these years early breeding failed to
lead to recruitment. However, while ponds on clay soil filled from the
same early rains, they did not dry until larvas had metamorphosed.
H. POPULATION SIZE
Most frog apecies are not amenable to study at the population level
because populations are not discrete. All burrowing frogs and many
others can only be caught in large numbers when they are breeding and
those which have only a short breeding period give no opportunity for
estimates of population size by using a technique of mark and recapture.
However, in a discrete population of the burrowing frogs Hebioporus
eyrei which remained adjacent to the breeding sites at Lighthouse
Swamp. Rottnest Island, Lee (1967) studied marked animals outside
the breeding season. He estimated the population to comprise 202 adult
males (limits 110-294) and 78 adult females (limits 71-85) on 24 November 1956. Juveniles were not sampled at this time but at the same date
in 1955 these were estimated to number 2241.
An estimate of population size waa attempted on a small breeding
congress of Neobatrmhw pelobatoides at Attadale during 1981. Prior to
30 June 1961, no water was present, no breeding had taken place and
Neobatrmhw could not be found. On the night of 30 June, 16 males
and 2 females of N . p e b b a t o i k were individually marked by toe clipping. Over the nighta of 1, 2 and 3 July, breeding continued and a total
of 75 males and 10 females were marked. On the night of 4 July there
was no breeding and neither males nor females could be found in the
vicinity. No female waa recaptured. The population estimate based on
the males recaptured on the fourth night waa 116 (Main, unpublished).
An attempt to follow the success of this breeding was frustrated when
the are(, was developed as a housing estate before recruitment oould be
measured. In subsequent years it has proved impossible to find a similar
discrete population of this specie8 on which to m w u r e reproductive
success aqd longevity.