The Robber Crab *Birgus latro* (Linnaeus, 1767)

*Selvaraj Kumaralingam*

#### **Abstract**

The robber or coconut crab *Birgus latro* (Linnaeus, 1767) is a terrestrial hermit crab. It is the largest—land living arthropod in the world. As far as India is concerned, distribution of this crab is restricted to Great Nicobar Island and South Sentinel Island in Andaman and Nicobar Archipelago. The crab divided into a front section (cephalothorax), which has eight legs, and an abdomen. The front-most pair of legs has large chelae (claws), with the left being larger than the right. The next two pairs, as with other hermit crabs, are large, powerful walking legs with pointed tips, which allow coconut crabs to climb vertical or overhanging surfaces.

**Keywords:** *Birgus latro*, Nicobar, India, robber crab

#### **1. Introduction**

The robber or coconut crab (*Birgus latro*; Linnaeus, 1767) is a terrestrial hermit crab. It is the largest—land living arthropod in the world. As far as India is concerned, distribution of this crab is restricted to Great Nicobar Island and South Sentinel Island in Andaman and Nicobar Archipelago. In the Nicobar Islands the species has been reported from Car Nicobar [1], Little Nicobar, Katchal, Camorta and Great Nicobar [2]. The crab separated into a visible section (cephalothorax), which has eight legs, and an abdomen. The next two pairs, as with other hermit crabs, are large, powerful walking legs with pointy tips, which allow coconut crabs to climb vertical or overhanging surfaces. The fourth pair of legs is slighter with tweezer-like chelae at the end, allowing young coconut crabs to grip the inside of a shell or coconut husk to carry for protection; adults use this pair for walking and climbing. The last pair of legs is very small and is used by females to tend their eggs, and by the males in mating. In the present study, the general ecology of coconut crabs in around great Nicobar is focused.

#### **2. Methods**

Coconut crabs are generally "easy to collect" and most often hand picking is very effective in intertidal zones, Crabs can be preserved wet in 6–10% formalin for further study. Field photographs by using the following taxonomic identification keys [3].

#### **3. Results**

#### **3.1 Habitat**

Coconut crabs are viewed as a standout amongst the most earthly decapods; the crab is an all-around adjusted loner crab, it is diurnal and night-time in propensities. Coconut crabs live alone in underground tunnels and shake hole, contingent upon the nearby territory. They delve their very own tunnels in sand or free soil. During the day, the creature remains concealed to diminish water misfortune from warmth. While resting in its tunnel, the coconut crab shuts the passages with one of its hooks to make the clammy microclimate inside the tunnel fundamental for its breathing organs They live solely ashore, coming back to the ocean just to discharge their eggs.

#### **3.2 Size**

This large sized crab grows up to 40 cm long and 22 cm wide (single sighting observed).

#### **3.3 Feeding habit**

Adult coconut crabs feed on fruits, nuts, seeds, and the pith of fallen trees, smaller worms, crustaceans and molluscs. The species is popularly associated with the coconut, and has been widely reported to climb trees to pick coconuts, which it then opens to eat the flesh.

#### **3.4 Behavior**

These Hermit crabs have a series of complex physical movements to communicate with other crabs in different situations. They are active at night which makes it difficult to see slight differences in body motion. They raise a single leg out and above the rest of their body as a warning to keep away.

**23**

**Author details**

archipelago.

Selvaraj Kumaralingam

Andaman and Nicobar Islands, India

provided the original work is properly cited.

Zoological Survey of India, Andaman and Nicobar Regional Centre,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: marinekumar@gmail.com

*The Robber Crab* Birgus latro *(Linnaeus, 1767) DOI: http://dx.doi.org/10.5772/intechopen.88429*

Coconut crabs are terrestrial animals whose eggs are hatched at sea. The female once her eggs have been fertilized by a male crab, will release her eggs into the sea with a new moon and a spring tide, when the humidity and temperature are right. The number of eggs she releases be a great as 138,000. The species' only dependence on the sea is for releasing eggs, which hatch in contact with seawater; the planktonic larvae then migrate onto land where they develop into long-lived adults [4]. And migrate to the shoreline with other terrestrial hermit crabs. The coconut crab reaches sexual maturity around 5 years after hatching. They reach their maximum

South Sentinel Island and Nicobar Islands in the Bay of Bengal, Central Pacific Ocean, Ryukyu Islands, Coast of Tanzania, Tropics of Cancer and Northern and Southern limits of Capricorn mark, Australia, Madagascar and Mauritius Island.

The population of this crab is dwindling due to habitat loss as a cause of coastal development and exploitation by human for food. Large populations exist on the Cook Islands especially Pukapuka, Suwarrow, Mangaia, Takutea, Mauke, Atiu, and Palmerston Island. The coconut crab *Birgus latro*, characterized as Data Deficient on the IUCN Red List [5], is the largest land crab. In worldwide conservation and management strategies have been put in place such as ban on the capture of eggbearing females and avoid the hunting of non-egg-bearing adults having above carapace length 30 mm. In India the species protected under Schedule I category of Wildlife (Protection) Act, 1972. The Conservation needs of the coconut crab *Birgus latro* on the Nicobar Islands, India [6]. We recommend that more extensive surveys be carried out in all potential coconut crab habitats on the Andaman and Nicobar

**3.5 Lifecycle**

size only after 40–60 years.

**3.6 Distribution**

**4. Discussion**

#### **3.5 Lifecycle**

*Crustacea*

**3. Results**

**3.1 Habitat**

their eggs.

observed).

**3.3 Feeding habit**

**3.4 Behavior**

then opens to eat the flesh.

**3.2 Size**

Coconut crabs are viewed as a standout amongst the most earthly decapods; the crab is an all-around adjusted loner crab, it is diurnal and night-time in propensities. Coconut crabs live alone in underground tunnels and shake hole, contingent upon the nearby territory. They delve their very own tunnels in sand or free soil. During the day, the creature remains concealed to diminish water misfortune from warmth. While resting in its tunnel, the coconut crab shuts the passages with one of its hooks to make the clammy microclimate inside the tunnel fundamental for its breathing organs They live solely ashore, coming back to the ocean just to discharge

This large sized crab grows up to 40 cm long and 22 cm wide (single sighting

Adult coconut crabs feed on fruits, nuts, seeds, and the pith of fallen trees, smaller worms, crustaceans and molluscs. The species is popularly associated with the coconut, and has been widely reported to climb trees to pick coconuts, which it

These Hermit crabs have a series of complex physical movements to communicate with other crabs in different situations. They are active at night which makes it difficult to see slight differences in body motion. They raise a single leg out and

above the rest of their body as a warning to keep away.

**22**

Coconut crabs are terrestrial animals whose eggs are hatched at sea. The female once her eggs have been fertilized by a male crab, will release her eggs into the sea with a new moon and a spring tide, when the humidity and temperature are right. The number of eggs she releases be a great as 138,000. The species' only dependence on the sea is for releasing eggs, which hatch in contact with seawater; the planktonic larvae then migrate onto land where they develop into long-lived adults [4]. And migrate to the shoreline with other terrestrial hermit crabs. The coconut crab reaches sexual maturity around 5 years after hatching. They reach their maximum size only after 40–60 years.

#### **3.6 Distribution**

South Sentinel Island and Nicobar Islands in the Bay of Bengal, Central Pacific Ocean, Ryukyu Islands, Coast of Tanzania, Tropics of Cancer and Northern and Southern limits of Capricorn mark, Australia, Madagascar and Mauritius Island.

## **4. Discussion**

The population of this crab is dwindling due to habitat loss as a cause of coastal development and exploitation by human for food. Large populations exist on the Cook Islands especially Pukapuka, Suwarrow, Mangaia, Takutea, Mauke, Atiu, and Palmerston Island. The coconut crab *Birgus latro*, characterized as Data Deficient on the IUCN Red List [5], is the largest land crab. In worldwide conservation and management strategies have been put in place such as ban on the capture of eggbearing females and avoid the hunting of non-egg-bearing adults having above carapace length 30 mm. In India the species protected under Schedule I category of Wildlife (Protection) Act, 1972. The Conservation needs of the coconut crab *Birgus latro* on the Nicobar Islands, India [6]. We recommend that more extensive surveys be carried out in all potential coconut crab habitats on the Andaman and Nicobar archipelago.

## **Author details**

Selvaraj Kumaralingam Zoological Survey of India, Andaman and Nicobar Regional Centre, Andaman and Nicobar Islands, India

\*Address all correspondence to: marinekumar@gmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

[1] Hume AO. Contributions to the ornithology of India: The islands of the Bay of Bengal. Stray Feathers. 1874;**2**:29-324

[2] Daniel A, Premkumar VK. The coconut crab in the Great Nicobar Island. Journal of the Bombay Natural History Society. 1968;**64**:574-580

[3] Alcock A. Catalogue of the Indian Decapod Crustacea in the Collection of the Indian Museum. Kolkata, India: Zoological Survey of India; 1905

[4] Reese BS, Kinzie RA. The larval development of the coconut or robber crab *Birgus latro* (L.) in the laboratory (Anomura, Paguridae). Crustaceana Supplement. 1968;**2**:117-144

[5] Eldredge LG. *Birgus latro*. In: IUCN Red List of Threatened Species v. 2010.4. 1996. Available from: http://www. iucnredlist.org [Accessed: April 19, 2011]

[6] Patankar V, D'souza E. Conservation needs of the coconut crab *Birgus latro* on the Nicobar Islands, India. Oryx. 2012;**46**(2):175-178. DOI: 10.1017/ S0030605311000408

**25**

**Chapter 3**

**Abstract**

Ecology

Scyllarid Lobster Biology and

*Kari L. Lavalli, Ehud Spanier and Jason S. Goldstein*

focus further studies in this important group.

ecology, life history, behavior, fisheries

**1. Introduction**

The family Scyllaridae is the most speciose and diverse of all families of marine lobsters. Slipper lobsters are found in both tropical and temperate habitats with hard or soft substrates and at different depths, and exhibit a wide array of morphological, anatomical, and physiological adaptations. Among the 20 genera and at least 89 species constituting 4 subfamilies, only some members of 4 genera, *Thenus* (Theninae), *Scyllarides* (Arctidinae), *Ibacus* and *Parribacus* (Ibacinae), form significant fisheries because of their large size. While scientific information on these lobsters has increased considerably in recent decades, it is still limited compared with commercially valuable spiny and clawed lobsters, and is confined to a few key species. The present chapter presents the current available knowledge on the biology of scyllarids and attempts to point out where questions remain to help

**Keywords:** slipper lobsters, Scyllaridae, taxonomy, genetics, anatomy, physiology,

Slipper lobsters, family Scyllaridae (Latreille, 1825) have been known and described since the late 1700s and are considered part of the superfamily Palinuroidea that consists of spiny lobsters (Palinuridae), furry lobsters

genera with at least 89 extant species thus far recognized [3–6].

(Synaxidae), blind claw-footed lobsters (Polychelidae), and slipper or shovel-nosed or bulldozer lobsters (Scyllaridae) [1, 2]. The Scyllaridae are organized into four subfamilies (Ibacinae, Arctidiane, Scyllarinae, and Theninae) and comprise 20

Only four genera—*Scyllarides* (Arctidinae), *Ibacus* and *Parribacus* (Ibacinae), and *Thenus* (Theninae)—form any kind of significant fishery because these individual species tend to be large in size [7]. Of these four genera, *Scyllarides* (Gill, 1898) has been studied extensively due to their large adult size, which makes them economically important; their worldwide geographical distribution in tropical and subtropical habitats; and their numerous species (14) [1]. Considerable knowledge is also available for species within the genus *Thenus* because of some relevance in certain fisheries as well as the success in rearing these animals in aquaculture [8]. Research on other species generally arises with overfishing of and a shift away from sister species (generally palinurids) and thus always lags behind exploitation, which is problematic for the creation of sustainable fisheries. Although small in size, lobsters of the genus *Scyllarus* often become a minor target for fisheries (e.g., [9, 10]).

#### **Chapter 3**
