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Published: September 27th 2010
It was Sunday evening and I got a text from Paul’s wife Neryl, the text said the road has just been closed as apparently the crabs have started to migrate, and her and Paul were the last people down the road before the barricades were dropped.
I had told Neryl that there were plenty of crabs around when I was on my way home at about 3.45 and she said that a park ranger was out racking them off the road with a big plastic rake not that very long ago.
I was up and away, early Monday Morning, on the scooter, when I got to the section of road where the barricades were they were up, so I carried on carefully along the road, there were lots of Robber Crabs feeding of their squashed Red brothers bodies along my route.
I got in to work, nice and early and it was a full on as usual, throughout the day we received
e-mails from Parks and Wildlife services, re the Red Crab migration and have included some extracts in to this blog.
That evening we all had to go home a different way from
work, basically you had to take the long way back which was about 35-40 K’s instead of the usual 20.
It was quite enjoyable as it was a side of the island I had not seen before, but connected with some roads I had been on once or twice.
Again just before the end of the light of the day, the Jungles little old men, or large old men, the Robber crabs were making their appearances, and whilst going up a slight hill on the scooter a vehicle came over the brow of the hill and went straight over one of these animals.
When I say Straight over I do mean, “Straight over” a wheel each side, missing the creature, but scaring the poor thing nearly half to death.
I kid you not, these creature’s don’t move that fast at all, and this fella had a bit of a shuffle along and sort of sat that regaining it composure, I was so annoyed at the car driver that I sat their and looked back, he or she stopped about 200 mtrs down the road as I am sure it had registered what had happened, I didn’t manage
to get a number, but memorized the car as best I could.
Just before I got home, instead of turning right, I turned left towards the barriers that I had gone through, this morning, and they were down, there were quite a few Crabs just walking underneath the barrier as if to say, we are safe here, but not the amount of Red crabs I was hoping for, I get the feeling it was a false alarm.
This is a copy of the information receieved from Parks and Wildlife Services.
Most of Christmas Island’s adult red crabs begin their breeding migration to the sea as soon as the wet season rains have established. But we can never be sure when the wet season is
going to begin!
The crabs’ breeding timetable is fixed around the phases of the moon. Spawning (the dropping of their eggs into the sea) must occur before sunrise on spring tides during the last quarter of the moon, regardless of any other factor.
The timing of spawning is the only certain and predictable part of the whole migration; all
other stages of the migration will vary with the prevailing
weather.
The crabs will start their migration if there is enough time for them to complete their downward migration, mate and develop eggs before the next suitable spawning date.
The red crab breeding migration comprises a series of separate actions on the crabs’ part that follow on from one to the other in a programmed sequence. These separate actions in combination make up the breeding migration and one action will not occur unless the preceding action is accomplished
If there isn’t enough time for them to be able to do all of these things before the next
spawning opportunity, they will delay the start of their migration and attempt to meet the following month’s spawning date.
The first action that occurs is movement of crabs to the sea. The largest mass movement of crabs takes place in this first downward migration.
Males farthest inland start this movement and are progressively joined by more and more crabs (both males and females) as the movement progresses toward the sea.
When the crabs arrive at the shoreline, they dip in the sea to replenish body moisture and salts.
The male and female crabs then move back on to
the shore terraces where the males dig
burrows for mating.
Mating takes place and then the males again dip in the sea and then they will start their return migration.
The females remain behind in the mating burrows to brood their eggs. This takes a couple of weeks.
A day or two before the spawning date the females emerge from the breeding burrows
with ripened eggs and move to the shoreline where they again dip in the sea and then retreat to shade.
Before the turn of the high tide and just before dawn the females will again move to the waterline and around the turn of the tide they will drop their eggs into the sea. After they have
jettisoned their eggs the females commence their return migration.
The next phase of the breeding migration takes place in the sea.
The eggs that the females drop into the sea hatch immediately
into larvae.
They grow through several larval stages into tiny prawn-like animals called megalops.
After about 4 weeks the megalops emerge from the sea and they moult into baby crabs.
The baby crabs then move inland and settle at suitable localities.
Golden Bosun
Protecting her ChickThe successful emergence of baby crabs is unpredictable but is
incredible when large numbers emerge.
Some years very few, or none, emerge. After about 4 years growth crabs will take part in
the breeding migrations and the life cycle continues.
If the rains stop or peter out, the crabs will delay the start of their
migration, or, if they have started migrating, they will stop moving and stay wherever they are until the rains begin again.
It is rare that substantial rains will begin early enough in the year for a spawn during the last lunar quarter in October - but it has happened! Spawning in November or December are the more usual, which means that rain must commence in the preceding
month and continue.
All phases of the crabs’ breeding migration involve colossal numbers of crabs and usually occur all over the island.
If the rains continue, there is usually a second, and sometimes even a third, smaller, downward migration by crabs that did not join in the first migration.
When this happens it is possible to see crabs on return journeys mingling with the crabs on their downward migration.
It
Chick
A poor photo, but the best I could do, without to much disturbanc can become confusing for all concerned! We are sorry that we can not be more explicit about the timing of the start of the red crab migrations, but the weather as you know cannot be accurately predicted.
The best advice we can give is to be at Christmas Island during the last quarter of the moon in either November or December for the best chance of seeing something interesting
happening in the annual red crab migration.
If you are able to arrive earlier and to stay longer the more parts of the migration
sequence you will be able to experience.
Possible spawning dates for 2010/11 are:
2nd October · 1st or the 30th November · 30th December
Hey how about that, what an amazing article.
I can honestly say that there is a rhythm to the Island, what with work, and just our existence, here, believe me I am yearning for a Pizza and a Barefoot Raddler, but just having past the half way mark of have a little time before I can delve in to such luxuries
This week we had a big event for us, our company were celebrating
its first anniversary of winning the contract and a BBQ party was being held at the golf club and coaches had been laid on for the activities.
So with best bib and tucker, the ones who were going waited patiently for the coach to take us to the event.
Those who know me, know I am the worlds worst evening person, 5.00 am in the morning I am brilliant, 10.00pm at night I am useless, and on a Friday night as well after a busy week, I had to pace myself, just a couple of drinks and some food then sneak off to my bed was the plan.
The food that was put on was fantastic, a huge Barbeque with music, have I meantioned how cheap alcohol is on the Island, it is ridiculously cheap. Gin and Tonic $5.00 bucks at a golf club as well.
I managed until 11.15 and my eyes were hanging out of my head and I just had to get home fortunately, I caged a lift with a couple who were going my way.
Saturday is what I think to be the worst day on the Island for me, I get up do my washing, yesterday was 3 loads, then tumble dry it, whilst it is drying, I jump on the scooter and go down to settlement to fill the bike up at the islands only fuel station, I have to say it’s not that expensive, something like $1.84 per litre, about £1.12, considering we are on an Island 1600 miles from western Australia, I remember paying 2.84 in the Northern Territories once at the Heart Break Hotel.
Once the scooter is filled up, with the grand total of $5.81 I went off for some minor provisions, then go back and do my ironing for the forth coming week.
The cinema was on tonight at 7.30pm so it was dinner at the Skanky Ho before we went to the movies and again we opted to sit on the grass.
Tonight’s movie was Inception, I have to say I didn’t think much of it as it was a bit to dark for me, but still I was thee to make my own decision.
Sunday I went in to work, I was glad to be back , being busy again, in the thick of it.
When I came home, I went and had a look to see if our resident Golden Bosun was with her Chick, I quietly walked over and was horrified to see the cat alarm lying down, when I looked in to the nest, this gorgeous little white and grey chick stared back at me, waiting patiently for her mum to come back and feed her, I carefully resited the cat alarm, just in case.
Finally I was watch the news this evening and surfing is 95 years old, Hawaii's Duke Kahanamoku is singularly credited with popularizing surfing world-wide during the 1920s.
Well that’s all from this blog, hope you enjoyed it.
Andy
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Mrs KJ
non-member comment
Canberra
When are you coming home??