The Red-necked Keelback: Hong Kong's Only Venomous and Poisonous Snake

The red-necked keelback (Rhabdophis subminiatus helleri) is one of my favorite snake species in Hong Kong. With its olive-green body and a vivid red patch around its 'neck' area, this snake is both visually distinctive and relatively easy to identify compared with many other Hong Kong snakes. It is commonly found throughout the region in both forested areas, mountains, and even right in the city itself!

What makes the red-necked keelback especially captivating is a defense that seems almost fantastical: it is both venomous and poisonous, capable of producing a milky-white toxin sequestered from its preferred prey, toads.

My first encounter with the red-necked keelback happened under unusual and somber circumstances: I found a dead specimen while cycling along the Shing Mun River. Snakes often carry a reputation in Hong Kong that is quite undeserved, and it’s possible someone killed this one out of fear or misunderstanding. Yet life does have a way of circling back.

Recently, I was delighted to spot a juvenile red-necked keelback around the same area! This little snake had just finished consuming a substantial meal, so I'm hoping it lives a long and healthy life (max lifespan 10-15 years)!

This wonderful encounter reminded me how lucky I am to live in Hong Kong, where the city's wild side often feels surprisingly close to home. If you keep your eyes peeled, who knows what wildlife wonders you'll discover!

Neck patch: A prominent red or reddish-orange patch on the neck, often bordered or accented. This neck coloration is the most distinctive identification cue.

Body color and pattern: Olive-green to greenish-brown body with a generally smooth, lightly speckled or faintly patterned dorsal surface; the pattern can include darker spots or checkering along the flanks.

Yellow band: Juveniles have a yellow band (sometimes called a collar) between the red neck and the head. You can see this in the image above.

Scales and texture: Keel-like (ridged) dorsal scales give the back a subtly rough texture when touched or viewed up close.

Size range: Typically mid-sized, often around 70–90 cm in length, though individuals can be longer in some regions.

Behavior cues: Often semi-aquatic, favoring wetlands, streams, and ponds; may assume a defensive S-curve when threatened rather than fleeing immediately.

Habitat hints: Common in water-adjacent habitats such as rivers, streams, and damp woodland edges, particularly in areas where frogs and toads are present.

Movement and demeanor: Generally shy and tends to retreat rather than strike. May flatten its head when alarmed to appear larger.

When active: Red-necked keelbacks are most active during the day, but can also be seen at night. I have seen these snakes in bright sunshine and at dusk.

The red-necked keelback has venom that it can deliver through its rear fangs when it bites and chews on prey. In addition to venom, the red-necked keelback stores toxins from prey in its special neck glands. When threatened, these glands can release a milky or whitish secretion that contains these sequestered toxins. This makes the snake both venomous and poisonous, a rare combination among snakes in Hong Kong and nearby regions.

How the Venom Works

Nature of venom: The red-necked keelback is a rear-fanged venomous snake. Its venom can enter the body when the snake bites and chews, and it can cause significant local and systemic effects in some cases. However, the snake must bite for several seconds to envenomate a human and cannot typically do so with a swift, fast bite like front-fanged venomous snakes can.

Local effects: Bites can produce intense pain at the site, swelling, bruising, and bleeding. In some instances, there may be mild local tissue damage, but that is not universal and varies by bite and individual response.

Systemic effects: Beyond the bite site, envenomation can lead to general pain, dizziness, and, in more serious cases, shock or coagulopathy. There have been reports of renal impact in some envenomation scenarios, underscoring the potential seriousness of bites.

Severity: While there have been fatalities in the broader literature and case reports, such outcomes are rare and depend on factors like bite severity, amount of venom delivered, and the patient’s health. Prompt medical care markedly improves outcomes.

How the Poison Works

Source of toxins: The keelback feeds on toads and collects their toxins (bufotoxins) in specialized neck glands. This makes the snake not only venomous but also poisonous in a defensive sense.

Gland secretion: When threatened, the nuchal (neck) glands can release a milky or whitish secretion that contains these sequestered toxins. Contact with eyes or mucous membranes can be irritating or harmful, and ingestion or exposure to mucous membranes can provoke more pronounced reactions.

Poison Delivery Mystery: Poison secretion can be prompted if a predator grabs the neck of the snake, potentially exposing the toad-derived toxins stored in the glands. Some observations suggest that secretion can be elicited even without direct neck injury - perhaps through neck muscle contractions or other pathways - though the exact mechanism remains debated.

Human impact: The defensive toxins are not typically involved in a bite’s immediate effects, but they add a layer of risk in handling, handling injuries, or close encounters. Proper caution around the neck region is advised even when the snake appears calm.

The red-necked keelback plays a key role in shaping Hong Kong’s local ecosystem through its dual predation and defense strategies.

As a predator of amphibians, the red-necked keelback uses its potent venom to regulate frog and toad populations, which in turn influences the structure of wetland and riparian communities. By feeding on toads, it participates in controlling species that can become pests or disease vectors, contributing to the health of aquatic and near-water habitats.

Its defensive strategy, via the toxin-producing nuchal glands, deters predators and reduces predation pressure on the keelback itself.

1. If you are bitten by a snake in Hong Kong, stay calm and move away from the snake immediately to avoid further bites.
2. Call emergency services by dialing 999 right away, as timely treatment is crucial.
3. While waiting for help, keep the bitten limb as still as possible and positioned lower than the heart to slow venom spread.
4. Remove any tight clothing or jewelry near the bite to prevent swelling complications. Gently clean the wound with water, but do not cut, suck, or apply a tourniquet to the bite area.
5. If you can safely do so, try to remember or photograph the snake’s appearance to assist doctors in identifying the species and providing appropriate treatment.

1. If your dog is bitten by a snake in Hong Kong, treat it as a medical emergency and seek veterinary care immediately.
2. Keep your dog as calm and still as possible to slow the spread of venom, and avoid any attempts to apply tourniquets or manipulate the bite area, as these can worsen the injury.
3. If it’s safe, try to take a photo or note the snake’s appearance to help vets identify the species and provide the correct antivenom.
4. Transport your dog quickly to a veterinary hospital that stocks snake antivenom, such as CityU VMC (24-hour service), which are equipped to handle venomous snakebites.
5. Watch for symptoms like swelling, pain, weakness, or paralysis, and inform the vet immediately so they can prepare antivenom and supportive care.

Here is a list of vets that carry antivenom.