Population and General Biology of Non-Reproductive Colonies of the Monarch Butterfly, Danaus Plexippus (L.) (Lepidoptera: Danaidae) in New South Wales.

Abstract

Data were obtained on population and general biology of three non-reproductive overwintering colonies ofthe monarch butterfly, Danaus plexippus (Danaidae) during April-August in 1980,1981 and 1982 at a site near Camden in New South Wales. A mark, release and recapture study showed that the 1981 colony was largely stable and the 1982 colony was migratory. In 1980 and 1981 populations comprised less than 500 individuals but in 1982 a peak population of 3500 butterflies was recorded. Males were sexually active throughout clustering. Most females were mated but showed no ovarian development. Periods of flight and feeding activity were common. The condition of most butterflies did not deteriorate markedly during clustering. Comparisons between winter non-reproductive monarch populations in North America and Australia are discussed.

Reply to Nylin, Wickman & Wiklund regarding sex ratios of California overwintering monarch butterflies

“…We found neither a pattern of greater male bias during the early phase (autumn) of colony increase nor a decline in male relative abundance at peak population levels, which normally occur in late December (Table I). James (1984) reported similar data for two overwintering seasons at a site in Camden, New South Wales, Australia. Selective advantage of early autumn arrival by males (relative to females) at overwintering sites is questionable because the critical aspects of evol utionary stable strategy life-history theory is focused on the timing of diapause emergence prior to and/or during the reproductive phase (February to early March in the case of D. plexippus (L) at central coastal California over wintering sites).…”

First Population Study on Winter Breeding Monarch Butterflies, Danaus plexippus (Lepidoptera: Nymphalidae) in the Urban South Bay of San Francisco, California

“…Non-reproductive colonies formed by migrants and reproductive populations of monarchs co-exist during winter in the Sydney Basin, New South Wales, Australia [ 19 ]. First described in the late 1970s [ 20 , 21 ], winter breeding and non-breeding monarch populations still exist, sometimes side by side, in the Sydney Basin [ 22 ]. Importantly, monarch migration still exists in New South Wales, with migrants forming non-reproductive overwintering colonies.…”

Monarch Butterflies in Western North America: A Holistic Review of Population Trends, Ecology, Stressors, Resilience and Adaptation

“…Monarch populations in south-eastern Australia in the early 1960s overwintered as non-reproductive populations comparable to California (up to 40,000 butterflies/site) in the Sydney Basin, New South Wales [70]. Research on these populations during 1978-1984 showed the existence of synchronous reproductive and non-reproductive overwintering populations [71][72][73]. Coincident with this apparent shift in overwintering behavior was a fall in the size of overwintering colonies from 40,000 to a maximum of 3500 butterflies per site [72].…”

“…Research on these populations during 1978-1984 showed the existence of synchronous reproductive and non-reproductive overwintering populations [71][72][73]. Coincident with this apparent shift in overwintering behavior was a fall in the size of overwintering colonies from 40,000 to a maximum of 3500 butterflies per site [72]. This 90%+ decline in overwintering monarch populations was thought to have resulted from the loss of milkweed habitat, but it is possible that the shift towards winter-breeding was at least partly responsible.…”

“…Insects 2024, 15, 40 7 of 29 fall in the size of overwintering colonies from 40,000 to a maximum of 3500 butterflies per site [72]. This 90%+ decline in overwintering monarch populations was thought to have resulted from the loss of milkweed habitat, but it is possible that the shift towards winterbreeding was at least partly responsible.…”