Boiga irregularis
Silhouette: Alex Slavenko · PhyloPic
In 3 days ~10% in a week ~20%
The brown tree snake (Boiga irregularis), also known as the brown catsnake, is an arboreal rear-fanged colubrid snake native to eastern and northern coastal Australia, eastern Indonesia (Sulawesi to Papua), Papua New Guinea, and many islands in northwestern Melanesia. The snake is slender, which facilitates climbing, and can reach up to 2 metres in length. Its coloration may also vary, some being brown, green, or even red. Brown tree snakes prey on a wide range of animals, from invertebrates to birds and even some small mammals. It is one of the very few colubrids found in Australia, where elapids are more common.
Due to an accidental introduction after the events of World War II, this snake is now infamous for being an invasive species responsible for extirpating the majority of the native bird population in Guam. Currently, efforts are being made to reduce and control the population on Guam and prevent the snake from spreading to other locations. Researchers are employing various methods, including aerial baiting, to attempt to control the population, while multiple agencies continue to fund and support the species' removal.
The brown tree snake is a nocturnal, arboreal... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Litchfield National Park | 🇦🇺 Australia | |
| 2 | Daintree National Park | 🇦🇺 Australia | |
| 3 | Tangkoko Nature Reserve | 🇮🇩 Indonesia | |
| 4 | Raja Ampat | 🇮🇩 Indonesia | |
| 5 | Kakadu National Park | 🇦🇺 Australia | |
| 6 | Nitmiluk National Park | 🇦🇺 Australia | |
| 7 | Lamington National Park | 🇦🇺 Australia | |
| 8 | Springbrook National Park | 🇦🇺 Australia | |
| 9 | Royal National Park | 🇦🇺 Australia |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Sydney | 🇦🇺 Australia |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Melbourne Zoo | 🇦🇺 Australia | |
| 2 | Featherdale Sydney Wildlife Park | 🇦🇺 Australia | |
| 3 | Alexandra Park Zoo | 🇦🇺 Australia | |
| 4 | Port Moresby Nature Park | 🇵🇬 Papua New Guinea |
Rare
Under 5% of wildlife watchers report a Brown Tree Snake sighting in Sydney on a given day, based on 7 verified sightings from GBIF citizen-science data. It is the 38th most-seen of the 39 reptiles we can rate there. Over three days the chance rises to about 10%, and over a week to about 20%, if each day is a fresh chance.
Any time of year
In every month with enough records, under 5% of wildlife watchers report a Brown Tree Snake in Sydney on a given day, so our monthly data shows no clear season.
Between 7 and 10 pm
Across all the parks we cover, that three-hour window holds the most Brown Tree Snake sightings with a recorded time, and about 7 in 10 of them come between 6 pm and 6 am: it is seen both by day and at night.
Only Sydney, in our data
Sydney is the only city on Wallace's Line with enough records to rate Brown Tree Snake sightings: under 5% of wildlife watchers there report one on a given day.
GBIF citizen-science records
It is estimated from how often the Brown Tree Snake is recorded against all the reptiles logged in Sydney (7 verified sightings), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
