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Red crab

The red crab (Gecarcoidea natalis), commonly known as the Christmas Island red crab, is a vividly colored terrestrial land crab endemic primarily to Christmas Island in the Indian Ocean, with a smaller population on the nearby Cocos (Keeling) Islands. This species is renowned worldwide for its spectacular annual mass migration, during which tens to hundreds of millions of adults trek from inland forests to coastal beaches for breeding, creating a striking "red carpet" effect across roads and landscapes. With a population estimated at over 100 million on Christmas Island as of 2025, the red crab serves as a keystone species in the island's rainforest ecosystem, driving nutrient cycling through its foraging and burrowing activities.^[1] Physically, adult red crabs feature a rounded, bright red carapace reaching up to 12 cm in width, with males typically larger than females and both sexes possessing equally sized claws; sexual maturity is achieved at about 4–5 cm after 4–5 years.^[2]^[3] They inhabit diverse environments including rainforests, coastal terraces, and even urban gardens, where they live solitarily in burrows for most of the year, emerging primarily at night or during rainy periods to forage on a diet of fallen leaves, fruits, flowers, seedlings, and occasional carrion such as dead birds or snails.^[2]^[3] The breeding migration occurs during the wet season from October to December, timed to the lunar cycle and high tides, with crabs following established forest-to-coast routes that can span several kilometers.^[2] Males arrive first to excavate mating burrows, followed by females who mate and brood fertilized eggs under their abdomen for approximately 14 days before releasing up to 100,000 larvae into the ocean surf.^[3] The planktonic larvae develop in the sea for several weeks before settling on land as juveniles, which then migrate inland in vast numbers, turning the landscape red once more.^[2] This cyclical event not only sustains the species but also influences local biodiversity by reducing plant competition and dispersing seeds.^[3] Although not formally assessed by the International Union for Conservation of Nature, red crab populations have faced significant threats from invasive yellow crazy ants, which reduced the population by about one-third (an estimated 10–15 million individuals) in the early 2000s through toxic interactions.^[4] Conservation measures, including ant eradication programs by Parks Australia, have led to a dramatic recovery, with over 100 million individuals participating in the 2025 migration—marking one of the largest events in recent history.^[1]^[5] Ongoing challenges include habitat loss from mining and climate change impacts on migration timing, underscoring the need for continued protection of this iconic species.^[6]

Taxonomy and distribution

Taxonomy

The red crab (Gecarcoidea natalis) belongs to the kingdom Animalia, phylum Arthropoda, subphylum Crustacea, class Malacostraca, order Decapoda, suborder Pleocyemata, infraorder Brachyura, superfamily Grapsoidea, and family Gecarcinidae.^[7] Within this family of primarily semiterrestrial to fully terrestrial crabs, G. natalis occupies the genus Gecarcoidea H. Milne Edwards, 1837.^[8] The generic name Gecarcoidea combines Greek roots ge (earth) and karkinos (crab) with the suffix -oeides (resembling), reflecting the group's adaptation to land environments, while the specific epithet natalis (Latin for "of Christmas" or "birthday") alludes to its type locality on Christmas Island, discovered on December 25, 1643.^[8] Originally described as Hylaeocarcinus natalis by Pocock in 1889 based on specimens from Christmas Island, it was later reassigned to Gecarcoidea to better align with its morphological and ecological traits.^[8] As a member of the Gecarcinidae, G. natalis exemplifies the family's evolutionary transition from marine to terrestrial lifestyles, with ancestors likely originating from brackish or mangrove habitats in the Indo-West Pacific region.^[9] Phylogenetic analyses indicate that G. natalis diverged from continental relatives, achieving full endemism on Christmas Island and the nearby Cocos (Keeling) Islands through isolation, maintaining high genetic diversity and a large, stable effective population size with minimal drift over its history.^[10] This isolation is underscored by genetic distances (e.g., ≥1.08% in COI sequences) from other Gecarcoidea lineages, supporting its status as a distinct species adapted to oceanic island conditions.^[8] The genus Gecarcoidea includes two other recognized species: G. lalandii (H. Milne Edwards, 1837), which ranges widely across the Indo-West Pacific from East Africa to the western Pacific, often in coastal forests; and G. humei Keenan, 1996, a more localized form in the eastern Indian Ocean.^[8] In contrast to these, G. natalis exhibits extreme isolation, co-occurring sympatrically with G. lalandii and G. humei on Christmas Island yet remaining genetically and morphologically distinct, highlighting the role of island biogeography in gecarcinid diversification.^[8]

Geographic range

The red crab (Gecarcoidea natalis) is endemic to Christmas Island in the Indian Ocean, an Australian external territory, and the Cocos (Keeling) Islands approximately 900 km to the southwest, with no established populations elsewhere. This restricted range results from limitations in larval dispersal, as the species has an obligate marine larval phase lasting approximately three to four weeks, during which planktonic zoeae and megalopae develop before recruiting back to land; such a duration constrains long-distance oceanic transport sufficient to colonize distant islands or mainland areas.^[11]^[12] On Christmas Island, which spans about 135 km², red crabs inhabit a range of terrestrial habitats including upland rainforests on the central plateau, terraced plateaus with secondary vegetation, and coastal shore zones, where they burrow in moist soils to maintain humidity for gill respiration.^[13] In contrast, populations on the Cocos (Keeling) Islands occupy a much smaller total land area of roughly 14 km² across the atolls, with lower densities and more fragmented distributions primarily in forested interiors and limited coastal areas, reflecting the islands' flatter topography and higher human disturbance. Genetic analyses indicate that populations on Christmas Island and the Cocos (Keeling) Islands share a common ancestry, with individuals on North Keeling (part of the Cocos group) representing recent immigrants from Christmas Island, though ongoing gene flow remains limited due to the separation by ocean currents and the constraints of larval dispersal. Historically, there is no evidence of range expansion beyond these islands prior to human arrival, as the species has been isolated since the emergence of Christmas Island approximately 5 million years ago during the Pliocene epoch, fostering its endemic evolution in this remote oceanic setting.^[14]

Description

Morphology

The red crab, Gecarcoidea natalis, possesses an oval-shaped carapace that measures up to 116 mm in width, providing a robust protective structure essential for its terrestrial existence.^[15] This carapace features a thick, calcified exoskeleton with densely packed setae that facilitate moisture retention through a rebreather system, wicking water across the surface to prevent desiccation in arid conditions.^[16] The rounded-shouldered design encloses the respiratory organs, including lungs and gills, enhancing protection while supporting air exposure.^[15] The appendages consist of eight walking legs adapted for terrestrial locomotion and two equal-sized chelae (claws) used in feeding and defense.^[2] These chelae are symmetrical in healthy individuals but can regenerate if lost or damaged, a common trait in decapod crustaceans that allows functional recovery post-injury.^[17] Respiratory adaptations include an enlarged branchial chamber that functions as a branchiostegal lung, enabling efficient air breathing by maintaining high oxygen uptake through vascularized linings and moist gill surfaces.^[18] Sensory structures feature compound eyes mounted on movable stalks, which can retract into sockets for protection and provide wide-angle vision for navigating forested terrains.^[19] Sexual dimorphism is evident in abdominal morphology, with males exhibiting narrower abdomens and females displaying broader ones to accommodate egg brooding during reproduction.^[2]

Coloration and dimorphism

The exoskeleton of the red crab (Gecarcoidea natalis) is prominently bright red-orange, a coloration derived from astaxanthin, a carotenoid pigment common in crustacean shells that absorbs blue light and reflects red wavelengths.^[20] This vivid hue is the species' dominant trait, though variations occur, including occasional orange individuals and rare purple morphs, the latter likely arising from genetic mutations altering pigment binding or expression. Purple forms are exceptionally uncommon, observed infrequently within populations.^[21] Sexual dimorphism is pronounced, with males attaining larger body sizes and developing more robust, prominent claws that facilitate territorial disputes and courtship displays. In contrast, females are smaller overall, featuring a distinctly curved and broader abdomen that provides protection for brooding eggs, with each female capable of carrying up to 100,000 eggs per brood during reproduction.^[2]^[22] Coloration undergoes changes throughout the life cycle; post-molting, the newly formed exoskeleton initially appears faded or paler as pigments redistribute and the shell hardens, a process typical in crustaceans where dietary and physiological factors influence the intensity of hues. Juveniles exhibit even paler tones compared to adults, enhancing camouflage amid the leaf litter and detritus of the forest understory where they forage and hide from predators. The adult red coloration likely contributes to adaptive functions, such as aposematic warning against predators or thermoregulation by absorbing solar radiation in the dim forest environment, though these roles remain under study in relation to the species' terrestrial habitat.

Behavior and ecology

Daily behavior

Red crabs (Gecarcoidea natalis) exhibit primarily diurnal activity patterns, emerging from their burrows during the day to forage and interact with their environment while remaining nearly inactive at night, even under conditions of lower temperatures and higher humidity that might otherwise favor nocturnal movement. To prevent desiccation, they avoid direct exposure to sunlight, preferring shaded areas within the rainforest understory. During the dry season, lasting approximately 2–3 months from May to November, red crabs drastically reduce their activity, retreating into burrows for extended periods to conserve moisture and avoid dehydration.^[23]^[24]^[25] These crabs construct burrows in moist soil or within rock crevices to regulate humidity and serve as refuges from predators and environmental extremes, with depths typically reaching up to 0.9 m and consisting of a single entrance tunnel leading to a chamber. Burrowing behavior is solitary, with each adult occupying its own individual burrow year-round, except during the brief breeding period when interactions increase; burrow entrances are often plugged with leaves during the dry season to maintain internal humidity levels. This solitary habitation supports their overall low-energy lifestyle outside of reproductive events.^[23]^[26]^[27] Socially, red crabs are largely asocial and territorial, defending their burrows against intruders through aggressive interactions, such as physical confrontations involving claw grappling, particularly among males competing for space. Population densities in intact rainforest habitats, which receive high annual rainfall exceeding 2,000 mm, can reach 0.5–1.6 burrows per square meter, leading to density-dependent spatial arrangements where individuals maintain personal territories but form loose, non-cohesive groups influenced by resource distribution and moisture availability.^[28]^[29]^[30] For navigation and orientation, red crabs rely on olfaction to detect chemical cues in their terrestrial environment and vision to maneuver through complex forest undergrowth, with both senses adapted for land-based life. They show a strong behavioral response to humidity gradients, increasing activity and burrow excavation in moister conditions while restricting movements when relative humidity drops below critical thresholds.^[31]^[23]^[32]

Diet and foraging

The red crab (Gecarcoidea natalis) maintains an omnivorous diet dominated by plant material, including fallen leaves, fruits (such as those from Pandanus species), flowers, and seedlings, supplemented by dead invertebrates like snails and occasional carrion, as well as human debris such as discarded food waste.^[2]^[24] Unlike predatory crabs, G. natalis engages solely in scavenging and does not actively hunt live prey. Foraging occurs opportunistically, primarily during the day when humidity is higher or immediately after rainfall events that facilitate movement across the forest floor.^[29] The crabs employ their robust claws to tear and manipulate tough vegetation, transporting food items back to burrow entrances for consumption or storage.^[33] This behavior is most active during the wet season, aligning with peak litter availability. In the ecosystem, G. natalis functions as a crucial decomposer and nutrient recycler, removing and processing 30–50% of annual leaf litter in rainforest habitats, which concentrates organic matter and essential nutrients (such as nitrogen, phosphorus, and potassium) near burrows to enhance soil fertility.^[33] Their extreme abundance—often exceeding one individual per square meter—eliminates significant intra-species competition for resources, allowing efficient litter turnover without territorial conflicts.^[34] To digest cellulose-rich plant matter, G. natalis relies on symbiotic gut bacteria alongside endogenous enzymes like endo-β-1,4-glucanases produced in the midgut gland, enabling high assimilation rates of energy (up to 50%) and nitrogen from leaf litter.^[35] Water requirements are met predominantly through moisture in food sources, supporting their terrestrial lifestyle with minimal reliance on free-standing water.^[36] During the annual breeding migration, foraging diminishes as individuals prioritize energy conservation for the journey.^[34]

Predators and threats

The larvae of the red crab (Gecarcoidea natalis) face significant predation pressure in marine environments, where they are consumed by reef-associated fish such as snappers and large planktivores including whale sharks (Rhincodon typus).^[37]^[38] DNA analysis has confirmed that whale sharks actively feed on these planktonic larvae during spawning seasons near Christmas Island, potentially decimating entire cohorts in years of high aggregation.^[37] Adult red crabs, however, experience minimal natural predation on land owing to the island's isolation and their dominance in the terrestrial ecosystem, though occasional attacks by coconut crabs (Birgus latro) on juveniles and smaller adults have been documented.^[39] An invasive threat to red crabs stems from the yellow crazy ant (Anoplolepis gracilipes), introduced to Christmas Island in the late 20th century, which forms supercolonies and sprays formic acid on crabs to blind and kill them.^[40] This acid spray targets the crabs' eyestalks and joints, leading to rapid mortality; since 1995, these ants have killed an estimated 10–15 million red crabs, representing about one-quarter to one-third of the island's total population at the peak in the 2000s.^[40] Although biocontrol efforts using phorid wasps have reduced ant densities in recent years, the threat persists in untreated areas, with ongoing local impacts on crab survival; as of the 2025 breeding migration, over 100 million crabs participated, indicating significant recovery from earlier declines.^[4]^[5] Other anthropogenic threats include road mortality during the annual breeding migration, where vehicles crush hundreds of thousands of crabs annually prior to mitigation measures, particularly along coastal routes like Murray Road.^[41] Habitat loss from phosphate mining has further fragmented red crab territories, with historical clearing affecting up to 30% of the island's forest cover and reducing suitable burrowing sites essential for foraging and refuge.^[6]^[42] Red crabs employ defensive strategies adapted to their environment, including rapid burrowing into soil to evade disturbances and aggressive displays with their claws, where males often clash chelae-to-chelae to deter intruders or competitors.^[28]^[43] This low overall predation pressure on adults contributes to their exceptionally high population densities, allowing tens to over 100 million to inhabit the limited rainforest area without significant top-down control.^[2]

Reproduction and life cycle

Breeding migration

The annual breeding migration of the red crab (Gecarcoidea natalis) is a synchronized mass movement that begins in October or November at the onset of the wet season on Christmas Island. This event is primarily triggered by the first significant monsoonal rainfall, typically amounting to at least 22 mm, combined with rising humidity levels that alleviate the dry season dormancy.^[44] The migration aligns with the waning moon phases, particularly the last quarter to new moon, ensuring that spawning coincides with milder neap tides for optimal larval dispersal.^[22] In scale, this phenomenon involves 40 to 100 million adult crabs undertaking journeys of 1 to 5 km from inland rainforests to coastal spawning grounds, with migration paths spanning approximately 20% of the island's suitable habitat.^[45] Larger males initiate the migration ahead of females, leading the procession in a generally direct route toward northwest shores, often halting briefly to feed and replenish energy.^[45] The sheer volume disrupts local traffic and ecology, as crabs traverse roads, cliffs, and streams en masse. At the coast, males compete fiercely through combat to claim burrows on shore terraces, establishing dominance for mating opportunities.^[45] Successful males mate with females in or near these burrows; afterward, females extrude and fertilize eggs, becoming berried and incubating them for approximately 12-14 days before releasing up to 100,000 larvae into the sea surf at high tide during pre-dawn hours.^[46] Prior to migration, red crabs accumulate substantial fat reserves during the dry season to fuel the energy-intensive trek, as they remain largely inactive and burrow-bound from April to October.^[45] Berried females, in particular, abstain from eating for several weeks during incubation, depending on these stores not only for the return journey but also to maintain egg viability until release.^[45]

Larval development

Females of Gecarcoidea natalis brood up to 100,000 eggs beneath the abdomen in coastal burrows for approximately 12-14 days until they are ready for release.^[46] The brooding period allows embryonic development in a protected terrestrial environment, with females remaining inactive to conserve energy during this phase.^[34] Upon immersion in seawater during neap tides, the eggs hatch immediately into zoea I larvae, which are swept offshore by currents.^[47] These planktonic larvae undergo five zoeal instars over 3-4 weeks, feeding on phytoplankton while dispersed in ocean waters.^[48] Following the zoeal phase, they molt into the megalopa stage, a more mobile, shrimp-like form capable of swimming toward coastal cues.^[49] Megalopae settle on Christmas Island's shores, guided by tidal rhythms and chemical signals from the intertidal zone, typically achieving 1-5% overall survival through the planktonic period due to dispersal by currents and intense predation.^[50] Upon settlement, they rapidly metamorphose into the first juvenile crab instar and burrow into moist soil within days, initiating the shift to a fully terrestrial lifestyle.^[51] This brief marine dependency contrasts with the species' otherwise land-based existence, ensuring genetic mixing across the island.^[34]

Growth and lifespan

Juvenile red crabs, Gecarcoidea natalis, undergo slow growth following settlement on land, with multiple molts occurring during their early phases to accommodate increasing body size.^[46] They reach sexual maturity at approximately 4–5 years of age, when the carapace width measures around 40 mm.^[46] In adults, growth continues at a reduced rate, with molting frequency declining to once per year, typically between January and March within the safety of burrows.^[52] This annual ecdysis supports incremental size increases, allowing individuals to attain a maximum carapace width of up to 116 mm.^[46] Females participate in breeding migrations annually after maturation, potentially reproducing multiple times over their lifetime.^[53] The lifespan of G. natalis is estimated at over 20 years, reflecting the species' slow growth and long-lived nature typical of terrestrial gecarcinid crabs.^[52] Molting and overall growth are influenced by environmental factors, particularly humidity and rainfall; surface activity and ecdysis are minimal below 77% relative humidity and peak above 95%, with the wet season facilitating these processes.^[52]

Population and conservation

Population estimates

Historical population estimates for the Christmas Island red crab (Gecarcoidea natalis) indicated approximately 43.7 million individuals in the 1990s, based on density surveys ranging from 0.09 to 0.57 adult crabs per square meter across the island's 135 square kilometers of suitable habitat.^[34] By the early 2000s, this figure had risen to around 55 million, reflecting stable conditions prior to major ecological pressures.^[54] The population experienced a significant decline due to the invasion of yellow crazy ants (Anoplolepis gracilipes), which formed supercolonies and preyed on juvenile and adult crabs, resulting in an estimated loss of 20 to 30 million individuals (up to two-thirds of the population) by the mid-2010s, bringing totals to around 15 to 25 million on Christmas Island.^[55]^[56] Less precise data exist for the Cocos (Keeling) Islands, where the species occurs in smaller numbers, estimated at 1 to 2 million individuals historically, though comprehensive surveys remain limited.^[57] Population assessments rely on quadrat sampling to measure crab densities in forest habitats and counts during annual breeding migrations to extrapolate island-wide totals, with Parks Australia conducting ongoing annual monitoring to track changes.^[58] These methods provide representative snapshots, as full censuses are impractical given the crabs' terrestrial distribution across rugged terrain. As of 2025, estimates for the Christmas Island population range from 100 to 180 million individuals, with over 100 million participating in the annual migration, supported by densities consistent with or exceeding pre-decline levels in monitored areas.^[54]^[5] On the Cocos (Keeling) Islands, estimates remain around 1 to 2 million, with no major shifts reported. Post-2015 trends show a steady increase of about 10 to 20 percent annually on Christmas Island, attributed to effective invasive species management, though recruitment variability linked to climate factors like rainfall patterns continues to influence yearly fluctuations.^[5]^[59]

Conservation efforts

The Christmas Island red crab (Gecarcoidea natalis) has not been formally assessed by the International Union for Conservation of Nature (IUCN) for inclusion on the Red List, though ongoing threats from invasive species have prompted calls for evaluation in recent reviews.^[57] Conservation efforts prioritize mitigating these risks, with significant focus on controlling the invasive yellow crazy ant (Anoplolepis gracilipes), which forms supercolonies that directly harm red crabs by blinding them with formic acid sprays and disrupting forest ecosystems. Since 2009, aerial baiting with low-concentration fipronil has been deployed across affected areas, achieving reductions of up to 99% in ant densities within supercolonies while minimizing non-target impacts on native species like red crabs.^[60]^[61] To transition from chemical to sustainable methods, biological control agents were introduced in the 2010s, including the micro-wasp Tachardiaephagus somervillei from Malaysia in 2016, which targets the lac scale insects that yellow crazy ants farm for honeydew, thereby starving ant colonies without broad ecological harm.^[62]^[63] These measures have contributed to red crab population recovery, with estimates ranging from 100 to 180 million individuals as of 2025—more than doubling from a decade prior.^[5]^[54] Habitat protection is anchored by Christmas Island National Park, which encompasses approximately 63% of the island's 135 square kilometers and safeguards critical red crab forest and coastal breeding grounds from development.^[64] Phosphate mining, a historical threat to habitats, has faced expanded restrictions, including the rejection of exploration proposals in 2018 due to potential significant impacts on ecosystems, with remaining leases set to expire by 2034.^[65]^[66] Monitoring and research efforts include annual tracking of red crab migrations by Parks Australia to assess population health and migration patterns, alongside climate modeling studies examining threats like altered rainfall and rising sea levels.^[67] For instance, a 2025 study found that reduced salinity from potential sea-level rise does not significantly disrupt embryonic development, though broader impacts on migration timing remain a concern.^[68]

Human interactions

Infrastructure impacts

The annual breeding migration of the Christmas Island red crab (Gecarcoidea natalis) frequently intersects with over 20 roads on the island, leading to significant vehicle-related mortality as millions of crabs cross paved surfaces to reach coastal spawning grounds.^[41] Historically, hundreds of thousands of red crabs have been killed annually by passing vehicles during peak migration periods, exacerbating population pressures alongside other threats.^[41] Recent conservation efforts have contributed to a decline in these figures, though exact counts remain challenging due to the scale of the event.^[5] To address these direct conflicts, various mitigation structures have been implemented since 2015, including at least five crab bridges, underpasses, and roadside barriers designed to guide crabs safely across roadways.^[69]^[70] These features, often elevated or fenced, allow migrating crabs to bypass traffic without altering their natural paths, and have been credited with reducing vehicle-induced mortality in targeted areas through diversion and protection.^[41] Complementary measures, such as temporary road closures and enforced speed limits during the October-to-December wet season migration, further minimize collisions by halting or slowing vehicular movement on high-risk routes.^[54] In 2025, during one of the largest migrations on record with over 100 million crabs, rangers used rakes to clear roads and innovative "crab mobiles" to gently steer crabs away from vehicles.^[5] The legacy of phosphate mining on Christmas Island has compounded these infrastructure challenges by creating fragmented habitats through historical clearings and excavations, which force crabs into narrower migration corridors and increase their exposure to roads and urban edges.^[6] These altered landscapes, spanning former mine sites now undergoing rehabilitation, disrupt traditional forest pathways and elevate vulnerability during mass movements, as cleared areas lack the vegetative cover that once shielded crabs from predators and obstacles.^[6] Annual "crab jams," where dense swarms of migrating crabs blanket roads and halt traffic for hours, underscore the scale of these interactions and necessitate coordinated traffic management to prevent widespread disruptions and additional fatalities.^[71]

Tourism and cultural significance

The annual red crab migration serves as a premier tourist attraction on Christmas Island, captivating visitors with the sight of millions of crabs traversing the landscape toward the ocean. In the 2023-24 financial year, approximately 5,741 tourists arrived by flight, many timing their visits to coincide with the November peak of the event, which transforms roads and forests into vibrant red pathways.^[72] Guided tours organized by local operators allow safe observation from elevated paths and viewing platforms, fostering eco-tourism while minimizing disturbance to the crabs; these experiences support small businesses and contribute to the island's economy through accommodation, transport, and interpretive services.^[73] As a keystone species, the red crab embodies Christmas Island's exceptional biodiversity and holds cultural resonance within the island's multicultural community, particularly among Chinese-Australians who associate the crabs' red hue with prosperity and good fortune during festivals. The migration has been prominently featured in Australian media outlets, including ABC News reports and Guardian articles that highlight its ecological spectacle, enhancing the island's profile as a natural wonder.^[74]^[5] Red crabs are not targeted for commercial fishing due to their small size—typically 115 mm wide—and unpalatable meat quality, which lacks sufficient flesh and flavor for human consumption. They are fully protected under the Christmas Island National Park management plan, where harvesting is prohibited to preserve the population and migration integrity.^[2]^[67] Parks Australia leads educational initiatives focused on the red crab's vulnerability to invasive species, such as yellow crazy ants, through guided walks, signage, and community workshops that emphasize conservation actions like ant baiting programs. Global awareness is amplified by documentaries and broadcasts, including a 2025 BBC video segment on the migration that reached international audiences.^[75]

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Red crabs in rain forest, Christmas Island: removal and relocation of ...
Jul 10, 2009 · Red crabs in rain forest, Christmas Island: removal and relocation of leaf-fall. Published online by Cambridge University Press: 10 July 2009.Missing: consumption | Show results with:consumption
[35]
Ecology and Behavior of Gecarcoidea natalis , the Christmas Island ...
Aug 5, 2025 · The terrestrial crab Gecarcoidea natalis is endemic to the forests of Christmas Island but must migrate each year to the coast to breed.
[36]
Widespread occurrence of endogenous cellulase production and ...
Sep 26, 2022 · ... Gecarcoidea natalis) can produce endogenous cellulases (Adachi et al ... It is possible that symbiotic gut cellulolytic bacteria may play a role ...
[37]
Dietary Assimilation and Food Retention Time in the Herbivorous ...
The ability of Gecarcoidea natalis to assimilate salts, nitrogen, energy, and fiber components from fallen leaves of Ficus macrophylla and Erythrina ...Missing: percentage | Show results with:percentage
[38]
Trophic and feeding ecology of whale sharks (Rhincodon typus ...
May 21, 2025 · DNA evidence of whale sharks (Rhincodon typus) feeding on red crab (Gecarcoidea natalis) larvae at Christmas Island, Australia. Mar ...
[39]
[PDF] The Dales Ramsar Site Ecological Character Description - DCCEEW
Meekan et al. (2009) confirmed whale sharks are feeding on the immature stages of red crabs.
[40]
Evidence for Active Predation on Red Crabs Gecarcoidea natalis ...
Birgus latro will also actively scavenge and has been observed to eat various carrion including the Christmas Island endemic red crabs Gecarcoidea natalis (Figs ...
[41]
[PDF] Crazy Ant Advice - DCCEEW
Since 1995, it is estimated that Yellow Crazy Ants have killed 10-15 million red crabs, about one quarter to one-third of the total island-wide population (P.T. ...
[42]
This Wasp Was Brought To Christmas Island In 2017—7 Years Later ...
Nov 22, 2024 · An ecological upheaval involving crazy ants killed millions of red crabs and threatened the survival of the species on Christmas Island, ...
[43]
Protecting Christmas Island's Iconic Red Crabs from Vehicles
... crabs. Unfortunately, hundreds of thousands of red crabs can be killed annually during their breeding migration by vehicles. In cooperation with key ...
[44]
[PDF] Christmas Island Flying Fox - Risk-based decision-support
Habitat loss Twenty five to thirty percent of Christmas Island has been cleared (mostly for mining), with high rates of clearing in the 1960s and 1970s, ...
[45]
Red Crab Males Fighting Over Burrow from Ardea
Male Red Crabs (Gecarcoidea natalis) engage in intense battles over burrows, crucial mating sites on Christmas Island from Ardea.
[46]
Christmas Island Red Crab Animal Facts - Gecarcoidea natalis
Christmas Island Red Crab Conservation Status. Least Concern. Christmas Island Red Crab Locations. Ocean · Oceania. Christmas Island Red Crab Locations ...
[47]
How red crabs on Christmas Island speak for the tropics
Oct 10, 2013 · The researchers found that the crabs largely only migrate if there has been at least 22 millimeters (0.87 inches) of rainfall. The crabs never ...
[48]
https://www.researchgate.net/publication/235654113_First_zoeal_stages_of_Epigrapsus_politus_Heller_and_Gecarcoidea_lalandii_H_Milne-Edwards_with_remarks_on_zoeal_morphology_of_the_Gecarcinidae_Macleay_Crustacea_Brachyura
[49]
https://core.ac.uk/download/pdf/11237028.pdf
[50]
Salinity does not affect late-stage in-egg embryonic or immediate ...
As a result, these species follow a strategy of larval export towards the open ocean, away from more variable coastal conditions (Torres et al., 2011). Larvae ...
[51]
First zoeal stages of Epigrapsus politus Heller and Gecarcoidea ...
Aug 6, 2025 · A series of typical morphological features is proposed for the zoea larvae ... stage of terrestrial recruitment, such as in Gecarcoidea natalis ...
[52]
[PDF] Zooplankton from the inshore waters of Christmas Island (Indian ...
with reference to larvae of the red land crab, Gecarcoidea natalis. C Davies1 ... has an obligate marine larval phase. Surface plankton tows, using a ...
[53]
Return to the land; The stages of terrestrial recruitment in land crabs
Aug 7, 2025 · Because the population showed a polymodal length frequency or multiple modes, the lifespan was estimated to be at least two years. Adult males ...
[54]
[PDF] Fun Fact Sheet: Christmas Island Red Crab | Marine Waters
The red crab, Gecarcoidea natalis, is a terrestrial (land) species of crab found almost exclusively on Christmas Island. The only other population of red crab ...
[55]
Burrow Dynamics of the Red Land Crab Gecarcoidea Natalis ...
Aug 7, 2025 · These movements are likely related to mating, saltwater drinking and foraging. The tracking patterns indicate that crabs form route memories.
[56]
https://humanprogress.org/more-than-100-million-red-crabs-migrate-on-christmas-island/
[57]
Millions of red crabs begin annual migration on Christmas Island as ...
Oct 21, 2025 · He said the red crab population was estimated to be about 55 million in the early 2000s, but was now approximately 100 million.
[58]
Christmas Island Red Crab Facts - ThoughtCo
Oct 27, 2019 · The Christmas Island red crab (Gecarcoidea natalis) is a land crab famous for its epic annual mass migration to the sea to spawn. Once numerous ...
[59]
[PDF] Christmas Island Yellow Crazy Ant Control Program - DCCEEW
The survey is based on a transect methodology where yellow crazy ant activity is measured every five meters along a 50 metre transect and red crab burrows are ...
[60]
The Epic Migration of 100 million Red Crabs on Christmas Island
Dec 9, 2024 · 100 million red crabs scuttle into every crevice of the island. Roads are closed to provide a safe passage for the crabs. They can even find their way into ...Missing: survey | Show results with:survey
[61]
[PDF] Biological control of crazy ants on Christmas Island - DCCEEW
Fipronil is highly effective at controlling crazy ants, but as Fipronil is poison, it can also kill other animals, like robber crabs, if not distributed.
[62]
Biological Control: A Christmas Miracle? | The Quagga
Dec 14, 2016 · Chemical Control An insecticide (FipronilTM) was dropped from helicopters into the supercolonies where it reduced crazy ant densities by 99.4% ...
[63]
Yellow crazy ant biocontrol - Christmas Island National Park
The formic acid that the ants produce at this density can wipe out entire local populations of endemic red crabs. Since the late 1990s, the invasive ants have ...
[64]
A tiny wasp could save Christmas Island's spectacular red crabs ...
Dec 1, 2016 · In the coming weeks, Parks Australia will release a 2mm wasp on Christmas Island to control the island's yellow crazy ant infestation.
[65]
Christmas Island National Park Management Plan 2014-2024
Jan 30, 2025 · Christmas Island National Park covers about 85 km2 (63%) of ... Red crabs are a keystone species. They maintain the structure and ...
[66]
Reprieve for Abbott's booby after Christmas Island mining expansion ...
May 31, 2018 · A report in 2010 found Christmas Island had been subjected to severe ecological stress triggered by land clearing for phosphate mining. The then ...Missing: loss | Show results with:loss
[67]
Christmas Island future uncertain as phosphate mine starts to wind ...
Jun 24, 2021 · The phosphate mine leases on Christmas Island end in 2034; A proposed marine park around the island would be bigger than the Great Barrier Reef ...
[68]
Red crab migration | Christmas Island National Park | Parks Australia
Red crabs all over the island leave their homes at the same time and start marching towards the ocean to mate and spawn. Male crabs lead the migration and are ...
[69]
Study explores effects of climatic changes on Christmas Island's red ...
Mar 11, 2025 · To understand that, the researchers exposed fertilised late-stage embryos of the crab (Gecarcoidea natalis) to four different levels of sea ...
[70]
Crab bridge helps Christmas Island critters beat the traffic - ABC News
Dec 8, 2015 · A five-metre-high bridge has also been constructed at one point along the road to help the crabs move across the island and continue their ...Missing: mitigation | Show results with:mitigation
[71]
Christmas cheer as the red crabs march begins - Ministers
Dec 24, 2023 · “To help the red crabs safely make their journey from the forest to the sea, national park staff install road barriers, crab bridges and ...
[72]
Millions of red crabs begin Christmas Island migration. - ABC News
Oct 21, 2025 · Christmas Island's unique red crab migration is underway with an estimated 100 million crabs making their way to the ocean. Christmas Island.Missing: bridges installed 2015
[73]
Clock is ticking: The Australian island facing an uncertain future - SBS
Apr 6, 2024 · According to the Christmas Island Tourism Association, 5,741 visitors arrived by flight in the last financial year, a figure that has held ...Missing: revenue | Show results with:revenue
[74]
Red Crab Migration — Christmas Island
Bright red is the common colour but there are the occasional orange specimens and more rarely some purple animals. They are a big crab. An adult body shell ...
[75]
https://www.bbc.com/news/videos/cx206pvyld5o
[76]
Watch: Christmas Island red crabs begin annual migration - BBC
Oct 23, 2025 · Tens of millions of crabs have begun their annual migration on Christmas Island, turning the roads and undergrowth into a carpet of red.Missing: mortality | Show results with:mortality