The period of the study included only one breeding season, and the majority of the animals marked were of adult size. Thus it has not been possible to follow the growth of an individual lizard from birth to adult size; however, sufficient information has been obtained from the 61 lizards recovered at least once to indicate the general pattern of growth. Table III presents the number of captures and recaptures, the greater number of lizards being taken in the summer period between the hibernations of 1954 and 1955.

As indicated in a previous section, parturition in 1955 took place from early January to early February, the majority of the young being born in the last week of January Some variation in the period probably exists between different years and in any one year within separate parts of the reptile's range.

A series of 19 newly-born young captured over three days at the peak of the parturition period averaged 0.276 gm weight (range 0.18 to 0.40 gm) and 27.6 mm long from snout to vent (range 24.5 mm to 29.0 mm). Six young born to one female in captivity averaged 0.265 gm (range 0.18 to 0.40 gm) and 24.8 mm long from snout to vent (range 24.5 mm to 25.0 mm).

Text-fig. 8.—Records of growth in Leiolopisma zelandica captured during the hibernation periods of 1954 and 1955. The figure alongside certain records refers to the detailed recapture data in Table V.

The most rapid growth occurs in the weeks immediately after birth; for example, a lizard (No. 118, Table IV) captured soon after birth when 25.0 mm long, showed an average gam of 0.17 mm and 0.007 gm per day over a period of 50 days. Two other juveniles (Nos. 87 and 95, Table IV) averaged 0.15 mm and 0.14 mm per day respectively in snout-vent growth, and No. 87 gained 0.007 gm per day in weight, but No. 95 showed no weight increment. Another juvenile (No. 93, Table IV) marked soon after birth at a snout-vent length of 25.5 mm was recaptured 243 days later in the following spring when 37 5 mm in length and three and a-half times its former weight. The slight increase in length of only 2.0 mm for this lizard, when compared with No. 87, which was first marked on the same day at the same snout-vent length but recaptured after only 68 days at a length of 35 5 mm, indicates that the initial rapid growth does not extend over the hibernation period. One lizard (No. 79, Table IV) was 29.5 mm in snout-vent length when captured on January 29, 1955, and on recapture 35 days later it was 38 5 mm. It can be assumed that this lizard was of average size when born, and from this it can be estimated that the time of birth was probably in the first week of January, so that its size on entering hibernation would be at least 45.0 mm. The size range of juveniles entering their first hibernation is from 30.0 to 45.0 mm, with most lizards between 35.0 and 40.0 mm.

Text-fig. 9.—Records of growth in all the individual skinks marked and subsequently recaptured one or more times. The figure alongside certain of the records refers to the detailed recapture data in Tables IV (Juveniles), VI (Sub-adults) and VII (Adults).

There is little or no growth of the lizards during hibernation as shown from measurements of a small number found while hibernating (Text-fig. 8; Table V). This period is not included in the graphs showing the growth rates of marked animals subsequently recovered. The length of the hibernation period omitted is based on the observed activity of the lizards within the study area.

The young lizards reach adult size 50.0 mm in snout-vent length during their second summer following their first hibernation. Very few young lizards were caught and only one recovery after a long term was made (No. 37, Table VI). This lizard averaged 0.085 mm per day increase in snout-vent length and 0.009 gm per day increase in weight for 165 days between hibernations, and reached an adult size of 51.0 mm when about 16 months old. Three other short-term recoveries (Nos. 41, 50 and 127, Table VI) showed similar trends in growth, respectively averaging 0.11, 0.087 and 0.062 mm per days increase in snout-vent length.

It is not clear whether the small number of sub-adult lizards captured was due to the few young surviving from a previous unrecorded breeding season, or to their more secretive habits. The lizards reach adult size over the brief span of 3 to 4 months in the first half of their second season of growth, and in these, the months of October, November and December, the vigorous plant growth of early spring provides much concealing cover which does not allow the young lizards to be readily caught.

The different growth rates of both the juvenile and sub-adult lizards leads to the loss of identity of the age-size groups as some of the lizards approach small adult size. Overlapping in size may occur between lizards 14 to 16 months old and individuals with retarded growth a year older. A rapidly growing juvenile (such as No. 79, Table IV) could attain a length of 45.0 mm at the end of its first season of growth, and be at least 55.0 mm long by the end of its second season of growth, when two years old. The group of lizards marked when about 55.0 mm in snout-vent length (Nos. 22, 51, 39, 67 and 54, Table VII) could include one or more lizards that reached large sub-adult size in their first season of growth. Despite the possible overlap these are in the main lizards in their third season of growth from 19½ months to 27 months old. The lizards above 55.0 mm in snout-vent length, that show a much slower rate of growth (Nos. 14, 17, 8, Table VII) are in their fourth season of growth, being 31½ to 39 months of age.

The average rates of growth of lizards for successive size increments has been calculated from all the recoveries shown in the graph (Text-fig. 9), and are presented in Table VIII. As the size group 55.0 to 59.9 mm includes lizards in both their third and fourth (and perhaps fifth) season of growth, two different rates of growth are evident. The averages for this size class have been calculated separately and as for other size classes the hibernation period of four and two-thirds months has been subtracted where necessary from the time elapsed between captures. The growth rates for each size class include those of some individuals that were recorded as growing through one or more size classes between captures which may produce inaccuracies in the average rates recorded.

The average growth rates are graphed in Text-fig. 10, together with a small number of individual recoveries which illustrate typical growth trends in relation to the calculated average. In order to obtain the time in months that it takes for a lizard to grow through a particular size class, the average monthly increment in millimetres for the lizards of a particular class was divided into the total increment within the size class. The periods of growth and hibernation with the sizes at different ages are included to provide a general picture of the growth of L. zelandica.

Text-fig. 10.—The average growth rate for successive size increments in Leiolopisma zelandica based upon the records of the skinks marked and subsequently recaptured. The unbroken lines accompanied by a number are individual recoveries (Tables IV, VI and VII) included to show typical growth trends in relation to the calculated averages (Table VIII).

Some lizards may fail to reach adult and breeding maturity by the time of emergence from their second hibernation. No direct evidence of this was obtained; the growth trend of one short term recovery (No. 50, Table VI) indicates that this lizard may have been no more than 45.0 mm long on entering its second hibernation. Individuals differ in their rate of growth, some continuing to grow rapidly until above average adult size and others ceasing rapid growth when below average adult size. The time of birth is critical in that it decides the maximum size that the

lizard reaches before entering its first hibernation. Similarly an extended autumm, allowing a longer first growth season, would show itself in later years by the presence of larger than average adults within any one age class which could only be separated from older lizards by their faster rate of growth.

The age-size classes of the population of L. zelandica studied (as represented by the average growth rates of those lizards recaptured) are thus not distinct from one another. The only readily identifiable group are lizards in their first year less than 46.0 mm in snout-vent length. A typical lizard (based upon the average rates of growth for successive size increments) attains 35.0 mm in snout-vent length at the commencement of its first hibernation when two and a-half months old. Growth ceases during hibernation and in its second growing season the juvenile reaches 45.0 mm at the end of one year and 50.0 mm at fourteen and a-half months of age, at which size the lizard enters hibernation for the second time. In the third growth season the lizard reaches 55.0 mm in snout-vent length when about twenty-two months old. Above 55.0 mm two rates of growth are apparent, the faster growing lizards being adults in their third season of growth, and the slower growing animals adults four or more years of age. The average rates of growth for lizards of these two ages which mix within a single size group are calculated separately. A few individuals may reach 60.0 mm in length by their 26th month, but in general the lizards do not exceed 60.0 mm until they are at least 34 months of age. The lizards mature sexually after their second hibernation, when above 50.0 mm in snout-vent length and at about 20 months of age.

The weights of all the lizards handled from the study area, either once or as recoveries, are plotted against their snout-vent lengths in Text-fig. 11. The relation

Text-fig. 11.—The weights of all the skinks captured in the study area either once or as recoveries.