Golden lancehead

On average, B. insularis grows to a length of 70 cm (28 in) and 90 cm (35 in), and it is known to reach 118 cm (46 in).[3] The color pattern consists of a pale yellowish-brown ground color, overlaid with a series of dorsal blotches that may be triangular or quadrangular, broad or narrow, and alternating or opposite along the dorsal median. In captivity, this yellowish color often becomes darker, which may be the result of poor circulation caused by ineffective thermoregulation.[5] A banded pattern results when the pattern is opposite. The head lacks a well-defined post-orbital stripe. The belly is a uniform pale yellow or cream.[3] The name "lancehead" refers to the distinctive head shape of all snakes in the genus Bothrops, which is somewhat elongated and comes to a point at the nose.[6] B. insularis also has a longer tail than its closest relative, B. jararaca, which is most likely an adaptation to help the snake maneuver through the trees, and to eat larger prey like birds from a younger age.[6]

Because of the isolated habitat of B. insularis, and the lack of mammal prey species, the venom of B. insularis has evolved to be adapted to the prey species of the island, primarily native ectotherms, arthropods and migrating birds. As a result, their venom is more potent towards these groups than mammals, and becomes more potent as the snake matures.[7] Chemical analysis of the venom of B. insularis suggests that it is five times as potent as that of B. jararaca and is the fastest acting venom in the genus Bothrops.[5]

Because B. insularis is only found in an area uninhabited by humans, there has never been an official report of a human being bitten by one, but other lanceheads are responsible for more human mortality than any other group of snakes in either North or South America.[3] Ludwig Trutnau reports four human envenomations, three of which were fatal. The mortality rate for lancehead envenomations is 0.5–3% if the patient receives treatment and 7% if the patient does not receive treatment.[3] The effects of envenomations by golden lanceheads include swelling, local pain, nausea and vomiting, blood blisters, bruising, blood in the vomit and urine, intestinal bleeding, kidney failure, hemorrhage in the brain and severe necrosis of muscular tissue.[8]

Bothrops insularis can usually be found either in the trees hunting for its prey, or seeking shelter among leaf litter or in rock crevices, especially during unfavorable weather or after having just ingested its prey.[5]

In Campbell and Lamar's 2004 accounts of the venomous reptiles of Latin America, there was no mention of any predators that could potentially prey on an adult B. insularis. However, the list of animal species provided by Duarte et al. includes several species of birds, spiders, millipedes, and various lizards that inhabit the island, which could potentially be predators of young snakes.[5] Of course, Duarte et al. also stress that there is a lack of observation of this species, due to the inaccessibility of the island Queimada Grande, and that just because a relationship between B. insularis and other species has not been observed does not mean that such a relationship does not exist.[5]

The golden lancehead's diet consists mostly of perching birds.[6] However, they have been reported to eat lizards, and even resort to cannibalism.[5] Newborn and juvenile golden lanceheads prey primarily upon invertebrates.[13] Adult B. insularis are able to survive off only one or two birds species per year of the more than 40 that visit the island.[14]

Adult Bothrops insularis are the only animals on the island of Queimada Grande that have been reported to eat birds.[5] There are other fauna, such as frogs, lizards, and birds, on the island that eat invertebrates, but because insects are so plentiful in ecosystems, they may not be a limiting resource. Therefore, studies would have to be done to determine whether or not juvenile and newborn golden lanceheads must compete for food with other fauna.

Golden lanceheads are known to suffer from flukes (specifically Ochetosoma heterocoelium) in their mouth cavity as well as carry the hard-bodied tick Ambylomma rotundatum.[5]

This species is classified as critically endangered (CR) on the IUCN Red List for the following criteria: CR B1ab(iii)+2ab(iii) (v3.1 (2001).[11] This means that the geographic range is estimated to be less than 100 km², that this area is severely fragmented or known to exist at only a single location, and that a continuing decline has been observed, inferred or projected for the area, extent and/or quality of the habitat. Furthermore, the area of occupancy is estimated to be less than 10 km². The population trend is stable. Year assessed: 2004.[15] The population of B. insularis on the island was estimated in 2021 based on a combination of observations, 2D, and 3D scanning of the island in 2015, and estimated to be between 2,414 (2D scan estimate) and 2,899 (3D scan estimate).[16]

Because the island on which the species is found is small, it can support only a small population, suggesting that the range between the number of snakes required for the population to survive and the maximum number the island can support is small, making the species especially sensitive to any other problems.[5] Also, because the island of Queimada Grande is the only place where B. insularis is found in the wild, if that population is wiped out the species will be extinct in the wild.

In the past, people have deliberately started fires on the island of Queimada Grande in an attempt to kill off B. insularis so that the island could be used to grow bananas.[5] The Brazilian Navy has also contributed to habitat destruction by removing vegetation in order to maintain a lighthouse on the island.[5] Because of these problems as well as overharvesting by overzealous scientists, Duarte et al. wrote that it is "very hazardous to assume that this is an invulnerable snake".[5] Based on a 100-year simulation, it was estimated that between 25 and 40 snakes harvested per year would cause genetic extinction for B. insularis.[16] Collection of this species of snake is permitted only with a scientific collection permit.

In addition to authorized collecting for research purposes, the illegal wildlife trade is a threat to B. insularis due to its rare nature, with researchers approached with offers of up to $30,000 for specimens in 2008, nearly 4 times Brazil's GDP per capita that year.[17]

Due to the small population and limited geographic distribution of B. insularis, there is a high level of inbreeding in the in situ population on the island. This threatens to produce deleterious genes in the population and is associated with extinction when inbreeding depression occurs in the population. Diversity management may be needed in the future for in situ and ex situ populations maintained off the island for research to avoid extinction.[18]

Associated with the heavy inbreeding of B. insularis is the occurrence of "intersexes", individuals born with both a hemipenis and female reproductive parts. Duarte et al. attribute these intersexes to "a great amount of inbreeding" within the population (which is another effect of the species' small distribution) and explain that the relatively high occurrence of intersexes being born may be harmful to the species population, since most of the intersexes are sterile.[5]

In addition to intersexes, it has been observed that when compared to their mainland relatives B. jaracara, B. insularis have reduced fecundity in females, and high levels of mutations in male sperm, thought to be a product of heavy inbreeding.[18]

As of 2019, it was reported by snake expert Bryan Fry, in an interview with 60 Minutes Australia that the migratory birds that B. insularis depends upon were visiting less due to deforestation on the Brazilian mainland.[19]