On every street you drive on in Ascension you will see a very funny street sign: Attention Landcrabs! Those crabs are the only indigenous animals on land and live in the mountainous are of Ascension. The first ones we see are running across our path during a short walk. They look relatively small until we find out that those are juvenile ones since a grown one is suddenly sitting in our way. The shell or carapace is about 10 cm wide and they are colored orange-yellow. They can stay underground for weeks waiting for rain, then they appear en masse. We are lucky since it is a cloudy day and we get to see more of them, sometimes standing in the middle of the street looking at our car. Now we know why they need those traffic signs. It is weird for us to look for crabs so far away from the ocean where they normally live. This is a good example for evolution where animals develop in a free niche. In the mountains the climate for the landcrabs is much better than at the coast because it is raining more often and therefor more humid as well as there is more vegetation around for them to feed on. They are omnivorous which means they eat plants as well as animals, but mostly they feed on leaves, fruits and flowers. They even eat their discarded shell to conserve calcium. In the Atlantic Ocean this landcrab species Johngarthia lagostoma lives on three more islands, Trinidade, Fernando de Noronha and Atol das Rocas (all belonging to Brazil).

23_Crabs_do_not_care_about_cars_but_we_should_take_care_of_them
23_Crabs_do_not_care_about_cars_but_we_should_take_care_of_them
24_The_landcrabs_(Johnghartia_lagostoma)_are_confined_to_the_mountainous_interior_with_higher_rainfalls
24_The_landcrabs_(Johnghartia_lagostoma)_are_confined_to_the_mountainous_interior_with_higher_rainfalls
25_Very_young_landcrab_hiding_under_wood
25_Very_young_landcrab_hiding_under_wood
26_Beautiful_male_landcrab_(Johngarthia_lagostoma)
26_Beautiful_male_landcrab_(Johngarthia_lagostoma)
27_All_crabs_we_found_were_male_because_the_females_are_alread_on_the_way_to_the_ocean_to_lay_their_eggs
27_All_crabs_we_found_were_male_because_the_females_are_alread_on_the_way_to_the_ocean_to_lay_their_eggs
28_Landcrabs_spend_most-of_the_day_in_burrows_coming_out_at_night_when_it_is_cooler
28_Landcrabs_spend_most-of_the_day_in_burrows_coming_out_at_night_when_it_is_cooler
29_Landcrab_looking_for_food_on_a_foggy_day
29_Landcrab_looking_for_food_on_a_foggy_day
30_They_can_stay_underground_for_weeks_at_a_time_waiting_for_rain
30_They_can_stay_underground_for_weeks_at_a_time_waiting_for_rain

Those landcrabs live their whole life far away from the sea and even though they still have gills they have become especially adapted for breathing air. They quickly drown if they are submerged in water. Only once a year the females walk many kilometers towards the ocean to lay their eggs. They gather in huge numbers creating a most impressive wildlife spectacle. After about two to three weeks the baby landcrabs called 'megalops' emerge from the sea and go on their journey towards the mountains of Ascension.

The amount of landcrabs decreased in the 19th century. They were eaten as well as hunted and killed because of their habit to eat the crops on Green Mountain. For every hundred pairs of claws the person would get a reward in form of money. If the landcrab population has recovered is not known at the moment. Predators and competitors such as rats, mice and rabbits that were introduced to the island by humans, continue to threaten the future of the landcrabs. At least against the rats you can find lots of rattraps around the island.

31_After_cats_were_introduced_on_Ascension_most_of_the_birds_only_nested_on_this_huge_rock_called_Boatswain_Island
31_After_cats_were_introduced_on_Ascension_most_of_the_birds_only_nested_on_this_huge_rock_called_Boatswain_Island
32_Boatswain_Bird_Island_where_most_of_the_birds_now_have_their_nests
32_Boatswain_Bird_Island_where_most_of_the_birds_now_have_their_nests
33_Brown_Booby_(Sula_leucogaster-Weissbauchtoelpel)
33_Brown_Booby_(Sula_leucogaster-Weissbauchtoelpel)
34_Masked_Boobies_(Sula_dactylatra-Maskentoelpel)_flying_at_Letterbox
34_Masked_Boobies_(Sula_dactylatra-Maskentoelpel)_flying_at_Letterbox
35_Masked_Booby_and_chick_at_Letterbox
35_Masked_Booby_and_chick_at_Letterbox
36_Almost_grown_chick_of_Masked_Booby_which_are_breeding_again_on_Ascension
36_Almost_grown_chick_of_Masked_Booby_which_are_breeding_again_on_Ascension
37_Ascension_Frigatebird_(Fregata_aquila-Adlerfregattvogel)_is_endemic_and_nests_mainly_on_Boatswain_Island
37_Ascension_Frigatebird_(Fregata_aquila-Adlerfregattvogel)_is_endemic_and_nests_mainly_on_Boatswain_Island
38_Juvenile_Ascension_frigate_bird_(Frigata_aquila)
38_Juvenile_Ascension_frigate_bird_(Frigata_aquila)

The rats and before that also the cats were responsible for decreasing the huge numbers of seabirds breeding on the island. Before the arrival of humans there were millions of breeding pairs on the main island. But because of the introduced predators they vanished and were only able to breed on the big rock called Boatswain Island. There are 11 species of breeding seabirds on the island. Next to the endemic Ascension Frigatebird (Fregata aquila) you can also observe the Masked Booby (Sula dactylatra), the Brown Booby (Sula leucogaster) as well as the White or Fairy Tern (Gygis alba) quite regularly. Fairy Terns are very curious and often flew above our heads during our walks. We could even see some chicks of Brown Boobies at the Letterbox Peninsula. This is possible because of the feral cat control programme which was introduced in 2001. They were able to catch all the cats and so the island was declared cat free in 2006. The first seabirds breeding on the island were Boobies as well as the Brown Noddies (Anous stolidus) and the Yellow-billed Tropicbird (Phaeton lepturus). It took a little longer for the Ascension Frigatebird to come back. The first two nests were spotted in 2012 on the Letterbox Peninsula followed by 44 breeding pairs in 2014. The numbers will hopefully continue to rise and therefore cameras were installed to observe the birds closely.

39_Poison_to_kill_all_the_rats_on_Ascension
39_Poison_to_kill_all_the_rats_on_Ascension
40_Young_Ascension_Frigatebird
40_Young_Ascension_Frigatebird
41_White_Terns_(Gygis_alba-Feenseeschwalbe)_are_also_called_Fairy_Terns_and_are_very_curious
41_White_Terns_(Gygis_alba-Feenseeschwalbe)_are_also_called_Fairy_Terns_and_are_very_curious
42_Old_image_of_visitors_between_the_huge_breeding_colony_of_Sooty_Terns_(Onchyprion_fuscata-Russseenschwalbe)
42_Old_image_of_visitors_between_the_huge_breeding_colony_of_Sooty_Terns_(Onchyprion_fuscata-Russseenschwalbe)
43_The_nocturnal_Band-rumped_Storm_Petrel_(Oceanodroma_castro-Madeirawellenlaeufer)_is_nocturnal_and_visited_our_boat_during_the_night
43_The_nocturnal_Band-rumped_Storm_Petrel_(Oceanodroma_castro-Madeirawellenlaeufer)_is_nocturnal_and_visited_our_boat_during_the_night
23_Looking_for_food_on_the_rocks
23_Looking_for_food_on_the_rocks
44_Some_Sally_Lightfood_crabs_(Grapsus_adscnsionis-Rote_Klippenkrabbe)_enjoying_the_waves_at_English_Bay
44_Some_Sally_Lightfood_crabs_(Grapsus_adscnsionis-Rote_Klippenkrabbe)_enjoying_the_waves_at_English_Bay

Once a year huge numbers of Sooty Terns (Onchyprion fuscata) come into Mars Bay to form a big breeding colony. And at some point close to Ascension we also had a guest on board. An exhausted nocturnal Band-rumped Storm Petrel (Oceanodroma sp.) took a break during the night. They still can not breed on Ascension because of the high number of rats. But all the rat traps will hopefully take care of this problem.

project manaia

Krüss Mikroskope