Boiga irregularis
Silhouette: Alex Slavenko · PhyloPic
In 3 days ~60% in a week ~90%
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 |
Possible
About 30% of wildlife watchers report a Brown Tree Snake sighting in Kakadu National Park on a given day, based on 27 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 9th most-seen of the 54 reptiles we can rate there. Over three days the chance rises to about 60%, and over a week to about 90%, if each day is a fresh chance.
March
In that month about 50% of wildlife watchers report a Brown Tree Snake in Kakadu National Park on a given day, against under 5% in December to February, the lowest months. That is one of Kakadu National Park's wettest months, with about 170 mm of rain against almost none in August.
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.
5th of 9
Of the 9 parks where we can rate Brown Tree Snake sightings, Kakadu National Park ranks 5th at about 30%. The best odds are in Litchfield National Park (Australia, about 40%), Daintree National Park (Australia, about 40%) and Tangkoko Nature Reserve (Indonesia, about 30%). All parks ranked.
Same family: Colubridae
The closest relatives of the Brown Tree Snake that you can see in Kakadu National Park (family Colubridae, Colubrid Snakes) are Mair's Keelback (about 30%), Black Treesnake (about 20%) and Slaty-grey snake (about 20%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Brown Tree Snake is recorded against all the reptiles logged in Kakadu National Park (27 verified sightings from 2019 to 2026), 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.
