Species → Southern Cassowary
Southern Cassowary
Casuarius casuarius
What if it disappeared?
Impact HighThe cassowary is the only animal able to disperse over long distances the seeds of more than 70 tree species in Australia's tropical rainforest, whose fruit is too large for any other forest animal to swallow.
DocumentedDetail
Wet Tropics Management Authority (gouvernement du Queensland). Cassowaries.
By swallowing whole fruit and then traveling several kilometers before defecating, the cassowary carries seeds far beyond the range of any other disperser in the forest — a service that no other animal of comparable size in this ecosystem could replace if the species were lost.
The last reliable census of the Australian population dates to 2012-2014; more than a decade later, no comparable survey has been repeated across the 9,000 km² of habitat involved, despite an explicit recommendation to do so — the current trend is therefore genuinely unknown, not merely uncertain.
ExtrapolatedDetail
Extrapolation prudente à partir du reportage Mongabay (mai 2026) sur le suivi de la population australienne de casoars — la donnée manquante elle-même, pas une étude publiée, est le sujet de ce point.
DNA sampling from droppings remains one of the few reliable methods to estimate population size at this scale, but deploying it across the full extent of Queensland's forest habitat remains expensive and logistically difficult in rugged, remote terrain — which explains, without excusing, the delay in the monitoring recommended since the 2012-2014 census.
What's missing to confirm it: An up-to-date census of the Australian population, methodologically comparable to the 2012-2014 one, to know whether the increase observed at the time has continued, stabilized, or reversed.
Even in forests fragmented by urbanization — that is, precisely where the species is most vulnerable — the cassowary continues to disperse native plant seeds; but in the most urbanized areas, a growing share of its diet consists of exotic rather than native fruit seeds, a sign the function is eroding before the bird even disappears locally.
DocumentedDetail
Campbell, M.A. et al. (2023). The southern cassowary (Casuarius casuarius johnsonii) remains an important disperser of native plants in fragmented rainforest landscapes. Austral Ecology.
By fitting cassowaries with an ingestible tracking device across four Wet Tropics sites with varying degrees of urbanization, the authors show that birds in the most intact forests feed exclusively on native fruit, while those in the most urbanized areas pass more exotic-species seeds in their droppings — the native-disperser function persists, but erodes with fragmentation.
Documentation
-
IUCN Red List — Casuarius casuarius, statut de conservation
Accessed August 14, 2026
-
Wet Tropics Management Authority — Cassowaries
Accessed August 14, 2026
-
Campbell et al. (2023) — The southern cassowary (Casuarius casuarius johnsonii) remains an important disperser of native plants in fragmented rainforest landscapes, Austral Ecology
Accessed August 14, 2026
-
Mongabay (mai 2026) — Amid efforts to save Australia's southern cassowaries, their numbers remain unknown
Accessed August 14, 2026
Last verified: August 14, 2026