On the oviposition of Homonota aff. darwinii in the Puna region of the Central Andes of Argentina

Abstract

Communal nest egg-laying refers to females laying their eggs with those of their conspecifics under or within artificial or natural structures. Homonota aff. darwinii is a recently discovered species that has not yet been formally described. The objective of this work is to characterise the oviposition of this species in the Puna region in the Central Andes of Argentina. We recorded the type and surface of the rocks where the eggs were laid, the temperature of the substrate, and the temperature of the rock surface facing the substrate. In addition, we recorded the daily temperature variation that a randomly selected potential spawning site would experience based on the characteristics of the rocks where the eggs were observed and the higher frequency of encounters with adult individuals. In January we found a nest with four hatched eggs under a rock. Later, in March we found two nests under two different rocks. One of the nests contained an unhatched egg, while the other nest contained an unhatched egg along with a hatched egg. Both unhatched eggs weighed 0.4 g and had a volume of 164.93 and 220.84 mm3. The embryo of one of the eggs was in an advanced stage of development, close to hatching. The rocks where the eggs were deposited were granitic and greyish. Each rock had a surface area of 768 and 1392 cm2, substrate temperature of 38.8 and 23.2 °C, and rock temperature of 35.5 and 24.9 °C, respectively. The potential nesting site registered a thermal amplitude of 15 °C (15–30 °C). It has been observed that H. darwinii in Patagonia has a one-egg clutch and an annual-biennial reproductive cycle, therefore, we hypothesize that the encounter of a nest with at least two unhatched eggs could indicate the occurrence of communal nests.