Hi Everyone,
As I watched a Beach Stone-Curlew eating small soldier crabs on Friday, it occurred to me that someone might have some knowledge about soldier crabs.
My question is: do soldier crabs form creches? And if so, for what purpose? And if not, why do they so frequently gather in these groups as described below?
Many times over the years, and now again, I am watching some very large soldier crabs gathering in large groups on the intertidal sandbanks in Noosa, SEQ. At the same time, only metres away, I also see large congregations of very much smaller soldier crabs, accompanied by a few very large crabs. I know nothing about the life cycles of crabs. It has always looked to me like the smaller crabs are being babysat by a few large ones whilst the adults are off at a party. Well, that’s the anthropomorphic interpretation :-), but there has to be an answer.
Cheers,
Jill
Thank you, Stephen, I shall continue this offline, as it is off-topic.
Jill Dening Sunshine Coast, Queensland, Australia
26° 51′ 41″S 152° 56′ 00″E
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) href=”mailto:birding-aus-request@vicnet.net.au”>birding-aus-request@vicnet.net.au
http://birding-aus.org ===============================
Hi Jill,
I have now found the scientific paper that I referred to in my previous email. It is:
Dittmann, S. (1998). Behaviour and population structure of soldier crabs Mictyris longicarpus (Latreille): Observations from a tidal flat in tropical North Queensland, Australia. Marine Biodiversity 28: 177-184.
Abstract
Crabs of the family Mictyridae are common on sandflats of the Indo-West-Pacific. Activity patterns and population structure of Mictyris longicarpus (Latreille) were monitored in the Haughton River estuary in northeast Australia. The emergence of the crabs at low tide was intermittent and could not be related to lunar cycles, but the crabs were significantly more active on sunny than on rainy or overcast days. Of a total of 1494 crabs measured over a 14 months period, nearly 2/3 were males (951 crabs). No ovigerous females were found on the sandflat surface. Crabs active on the sediment surface ranged in size from 4.7 to 19.7 mm carapace length (CL). Distinct size-frequency distributions were identified for juveniles, females and males. The mean size of juveniles was 7.3 mm and of females 11.2 mm CL. Males showed a bimodal size-frequency distribution. The first mode (mean 8.5 mm) was clearly separated in size from the second mode (mean 15 mm). The population structure remained almost constant throughout the year. Juvenile and adult crabs showed different aggregation patterns and preferred different sediment types.
Stephen Ambrose Ryde NSW
===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) href=”mailto:birding-aus-request@vicnet.net.au”>birding-aus-request@vicnet.net.au
http://birding-aus.org ===============================
Stephen, thank you for that reply. Even if you don’t find the paper, I shall have a good look at the sediments next time I’m out there. The theory makes some sense. Just thinking, I don’t think I have seen shorebirds, even Beach Stone-Curlews, take adult soldier crabs, though they take plenty of small crabs, which I always assumed to be immatures. The big ones could probably do some damage to a bird’s mouth as they fight for survival. Also not good energetics.
Cheers,
Jill
Jill Dening Sunshine Coast, Queensland, Australia
26° 51′ 41″S 152° 56′ 00″E
href=”mailto:birding-aus-bounces@vicnet.net.au”>birding-aus-bounces@vicnet.net.au ===============================
To unsubscribe from this mailing list, send the message: unsubscribe (in the body of the message, with no Subject line) href=”mailto:birding-aus-request@vicnet.net.au”>birding-aus-request@vicnet.net.au
http://birding-aus.org ===============================
Hi Jill,
I remember reading a scientific paper a few years ago (sorry, I can’t remember which one) which said that juvenile soldier crabs tend to congregate in large groups on different sediments to the larger adult soldier crabs. If I remember correctly, the smaller soldier crabs tend to congregate on the softer sands/muds (probably easier for them to excavate these areas), whereas the larger ones can use sandflats/mudflats that are more compacted and harder to excavate.
If I find the title of the paper I’ll send it across to you.
Stephen Ambrose Ryde, NSW