Xeromys myoides Thomas, 1889 (Rodentia; Muridae) in mangrove communities of North Stradbroke Island, southeast Queensland

29 Pages·1996·8 MB·

by  Steve Van Dyck

XEROMYSMY01DESTHOMAS, 889 (RODENTIA: MUR1DAE) IN MANGROVE
1
COMMUNITIES OFNORTH STRADBROKE ISLAND, SOUTHEASTQUEENSLAND
STEVEVAN DYCK
Van Dyck,S. 19960630:XeromyunyoidesJhon)^, 1889iRodentia;Muridae)inmangrove
communitiesofNorthStradbrokeIsland,southeastQueensland.MemoirsoftheQueensland
Museum 42(1); 337-366. Brisbane- ISSN Q079-SS35,
Sevenmangrovecommunities spanningthenorth-southlengthofwesternNorthStradbroke
bland were surveyed between 1991 and 1993 tor Xeromys ntytudes. It was recorded at ail
sues, btotal of 11 1 individuals was captured andhome rangeestimates andecological data
wen- recorded for nine individuals. The life history Df this small, spotted, specialised,
non-aquatic, non-arboreal, nocturnal rodent revolved around the island's mangrove and
adjacent sedgelandcommunities. It nestedineitherlargetermitanum-likemoundsorsimple
tunnels in the supralittoral bank. Nests contained up toeight individuals ofall age groups
and either sex. with one adult male present in the resident group. From their nests, rats
followedtherecedingtideoutthroughsedgclandandintothemangroveswheretheyforaged
overahome rangeestimatedatapproximately0.8haformales and (-haforfemales. Home
ranges overlapped slightly, but core areas, estimated at around0.2ha,did not. Home range
suewasthoughttobedeterminedbythecomplexityofthemangrovecommunityasreflected
in the structural diversity of the mangrove substrain The diet Of X myoties consisted erf
smallcrustaceans mainly thecrabsParasesannaetythrodaciyluand Heineleachi), marine
I
polyclads. marine pulmonates and marine bivalves. The species was recorded in breeding
Condition throughoutmostoftheyear. Uisproposedthattheunusuallife-styleofthisrodent
mightbelinkedtoproblemsassociatedwiththeneedtodissipatehealratherthanthemvessity
to rctaftl it- Caution should be eveicised m attributing its locally abundant status on North
StradbrokeIslandtopopulationsonthemainlandwhichawailassessment..V.vvvnw, False
Wuter-rui, rcdents, mangmvex. North Stradbroke Island.
Steve Van I)\<k, Qitrrfi.\l<wd Mnu-aiti, PO BoxJSOO, South Brisbane, Queensland'4IQI,
Australia; 2()December 1996,
The False Water-ratXeromys myoidesThomas* trapped near one Of a number of reed-covered
1S89(Fig. 1) is a small, poorly known Australian peatmoundsInsedgelandsoftheMyorawetlands
hydrornyinerodent.Fourteen museumspecimens (Van Dyck, 1992, ^994; Van Dyck & Durhidpc.
are known (Van Dyck & Durbidge. 1992). These 1992).ThesereportscommentedonthesimiL
and other specimens liberated aftercapture, have oJ-lhe j^ lermuunum-!ike nesting mounds to
beencollected frommangroveforests,freshwater mat duajbed by Magnusson et at (1976) from
lago?ons,Wswamps^or sedged lakes close 10 Melville Island but, in addition, noted the pres-
e1973al;.,Redh9e7a6df,t&coMacskeaanc,en3t1r9Sa7l25;?QMSuaege(nnusslsaonnd' «i. r"*c.vs°hl'lwiau«.,e«rarWl-ww„bal,l»l]uAsttiiti.mMJp/l^l.ebhvc.ttun_mnr_naeeelt-fs,thtebCua-isi.lehtdJogfnie.nhlt.aoiimltudhs/e
Thomas. 1SS9; McDougall 1944) and coastal «*«*
psDoayuuctckhietaeysttpaflQ.,tuhei1es9n7rs9e)lc.aonrIdtdir(seDfnwol'evtcetkrsngeotewnanul.i,wnhe1e9tr7ah9re;irtvVtaohnre ™s!i«sm*cP«d,*c*)tu>nntchles *lo XIWn"teWntofIa*ti,*vare£llychcantPeLs°rrt*,b»nib.^titl™n«g>yuthn*edf*s
the inadequacy of searching effort in the appro- W appropnate habitat may not be a reliablegross
priate habitat, however the animal is currently indicator ol lhc absence ot .V. myoides,
Classified under theCommonwealth Endangered In an attempt jo Clarify the distribution al X.
SpeciesProtection Act 1992 as Vulnerable myoides in the mangrove communities of North
Xetomys myoides has been known from North Stradbroke Island, nest recording and (rapping
SatnraaddublrtokfeemIasllaendw.aQsuheaennds-leaanudehstinbcey 1s9tu7d8enwthseant sWu«rtvcf>Ss wnoorrethc-ownedsutcertleyd Itirpo,minoeaJrumApmiintpyino.n tthhee
Myora Springs (Van Dyck et al., 1979), This eland's southern extremity 36km south (Figs 2-
;imen represented the most southerly record 6)- Radiotclcmetry of animals trapped and re-
for the species. In 1992, Ellie Durbidge and I leased was expected to generate same
recorded the capture of another adult female preliminary information for the species on dici.
338 MEMOIRS OFTHEQUEENSLAND MUSEUM
FIG. 1. Xeromysmyoides, adult female from RainbowChannel, NorthStradbroke Island (Bruce Cowell).
home range, foraging behaviour and aquatic ad- chunks of chopped mullet or gar, were placed
aptation. among mangrove roots, beside trunks with base
hollows, among pneumatophores or inside hol-
METHODS low logs. Traps were not set up in trees.
Normal terrestrial trapping protocol was ad-
FIELDSURVEYS. Fieldobservationsandsurveys justed to accommodate threats ofdrowning im-
associated with this study were made between 3 plicit in the method. Live-trapping on the
Nov 1991 and 18 Nov 1993. Fieldwork prior to mangrove floorrequiredlocalknowledgeofboth
Sept 1992concentratedonnestappraisal,capture the upper inundation height of night high tides
and radiotelemetry ofindividuals at and near the and the rates of incoming tides as traps required
Rainbow Channel (site 2, Fig. 3), while the latter checkingandtrippingpriortotheirinundation. A
partdocumentedthepresenceofX. myoidesinsix rising tidecombinedwithtoomanytrapssetover
otherareasofmangrovehabitatalongthewestern a long mangrove transect (e.g., 75 traps over
side ofthe island (Figs 2-6). lkm) proved a drowning hazard to trapped rats
and a formidable task for one person in a night.
CAPTURE TECHNIQUES. Elliott (Elliott Sci- Loopingofmangrovetraplines(25trapsperloop)
entific, Upwey, Victoria) size Aaluminium traps north and south of a 'central' land-based camp
(300x100x90mm) were used. Up until Sept 1992 gave adequate coverage ofmangrove forest, and
trapping was conducted only at or near nesting quickeraccess to both traps and the station asso-
mounds, none of which was found constructed ciated with processing captures. Trapping was
inside the mangrove zone but in sedges of the carried out during the following periods: Nov
supralittoral zone. Thereafter, given the initial 1991 (8 trap nights); Feb 1992 (13 trap nights);
results of direct observation through radio- May 1992 (249 trap nights); June 1992 (29 trap
telemetry, traps were laid along the floor of the nights);July 1992 (196trapnights);August 1992
mangroveforest. Awhitecottonstring-lineguide (188 trap nights); September 1992 (263 trap
was laid simultaneously. Traps, baited with nights);October 1992(50trapnights);November
-
XEROMYSMYOIDESOFNORTHSTRADBROKE ISLAND
condition and individual traits
(tail kinks, albinism in tail-up.
ear damage etc.). Initial diffi-
culty in determining sex inju-
• veniles and sub-adults was
Chiggil Chiggil
MORETON resolvedusinga measureofthe
BAY j%RainbowChannel distance between the anus and
the urogenital opening Canal
jfcMyora Springs, genital distance') which was
/^TwoMile significantly less in females
^30 CITY (Table 2). X. myouies rarely
OF 1 struggled, andgavetheimpres-
BRISBANE £ Deanbilta sion of being almost incapaci-
NORTH tated by fear. However, when
ISTRADBROKE handled with ungloved hands
they indicted deep biles, so
, ISLAND
were restrained for measuring
through a cloth collecting bag
CanalpjnCreek rolledbacktogiveaccesstothe
animals. Dorsal spotting pat-
terns were recorded (Table 2t,
SOUTH and each animal was assigned
27"40" PACIFIC to an age category by weight:J
OCEAN (juvenile) <28g; SA (sub-
adult) 28-35g; A (adult) >35g.
Each animal was individually
tagged. Initially, animals were
tagged on one ear with a num-
bered brass lag (Hauptncr-
Ohramarken#73850)ora fish
& small mammal tag' (No.
153n20' 15330' 1005-1, size I, National Band
and Tag Co, Newport, KY).
FIG. 2.Sites(I-7)surveyed forXemmys myoticson NorthStradbrokeIsland. fBaoctthortyagantdypweesreprfoovuenddutnosahtaivse
been ripped from ears after a
1992 (50 irap nights); December 1992 ( 100 trap fewdays. Finally,asystemofcarnicks was used
n(i7g0httsr)a;pJniagnht1s)9;93Ma(v501t9r9a3p n(i5g0httsr)a;pMniagrhtcsh);1J9u9l3y A simple 2mm cut was made in the edge ofthe
pinnawithsmall surgicalscissorsdippedintattoo
1993 (40 trap nights); October 1993 (40 trap
nights); November 1993 (36 trap nights). Trap ink Using well-defined areas of the upper and
nights totalled 1480 and covered sites at Chiggil lower folds of the pinnae, a wide range ofiden-
Chiggil, Rainbow Channel, Myora Springs, Two tificatory combinations was available. Ear cuts
Mile. Deanbilla.Canaipin Ck and Stockyard (see healed and rejoined quickly, leaving a fine black
Table 1, Figs 2-6). line readily discernable when torch-illuminated
In openAvicetmia marina woodland such as at from behind the pinna.
Canaipin Creek, where old trees were widely Trapped animals were measured (Table 2) and
spaced and the substrate simple, it was possible released before dawn at theirpoint ofcapture, or
tospotlight forA', mxoidesamong pneumutophores their nest (where known). In cases where a nest
and capture them by hand. site was not known for an individual and the
No attempt was made to dig individuals from incoming tide had covered the capture site, the
nests and no nestingmounds were breached. animal wasdepositednearestthetrapsite in alow
mangrove hollow that provided cover and easy
HANDLING AND RADIO-TRACKING PRO- access to the ground. Animals responded pas-
CEDURES. Captured individuals were weighed, sively but poorly to being held over for measure-
measured, sexed, and assessed for reproductive ment during the day following theircapture, and
340 MEMOIRS OFTHEQUEENSLAND MUSEUM
[2] Avicenniamarinavaraustralasica Low-openshrubland,LowshrublandandOpen-heath
[3] Avicenniamarinavaraustralasica Tallopen-shmblandandTalishrubland
[4] Avicenniamarinavaraustralasica Open-scrub andClosedscrub
[5] Avicenniamarinavaraustralasica Lowopen-woodland,LowwoodlandandWoodland
[7] Avicenniamarinavaraustralasica Lowopen-forestandOpenforest
[18] Rhizophorastytosa Tallshrubland,Open-scrubandClosedscrub
y
Landsubjecttotidalinundationcomprisingsaltwatercouchandorsamphireflatsormarineclays
£]Landsubjecttopermanentorseasonalinundation
FIG. 3. Sites and vegetation types surveyed for Xeromys myoides on North Stradbroke Island at (1) Chiggil
Chiggil and(2) RainbowChannel (afterDowling, 1986).
XEROMYSMYOIDESOFNORTH STRADBROKE ISLAND 34
m
-Amty .Banks [kW \\ /I{.. I
[4] Avicenniamarinavaraustraiasica Open-scrubandClosedscrub
[5] Avicenniamarinavaraustraiasica Lowopen-woodland,LowwoodlandandWoodland
[7] Avicenniamarinavaraustraiasica Lowopen-forestandOpenforest
[18] Rhizophorastylosa Tallshrubland, Open-scrubandClosedscrub
fc]Landsubjecttotidalinundationcomprisingsaltwatercouchandorsamphireflatsormarineclays
[-]Landsubjectlopermanentorseasonalinundation
Scale.IZ5.000.
KILOMELTREfe
FIG.4.SitesandvegetationtypessurveyedforXeromysmyoidesonNorthStradbrokeIslandat(3)MyoraSprings,
(4)Two Mile and (5) Deanbilla (after Dowling, 1986).
342 MEMOIRS OFTHEQUEENSLAND MUSEUM
i i : i i
; PeOcsn Banks I
a
, . . j
Seagrass
:.:.
(3] Avicenniamarinavaraustralasica Tallopen-shrublandandTallshrubland
[4] Avicenniamarinavaraustralasica Open-scrubandClosedscrub
[5] Avicenniamarinavaraustralasica Lowopen-woodland, LowwoodlandandWoodland
[7] Avicenniamarinavaraustralasica Lowopen-forestandOpenforest
[-;)Landsubjecttotidalinundationcomprisingsaltwatercouchandorsamphireflatsormarineclays
j%]Landsubjecttopermanentorseasonalinundation
I
ME.TRE.S Scale I-2.S.OOO l-'ILCiMiLTR^C
FIG. 5. Sitesand vegetationtypessurveyedforXeromvsmvoidesonNorthStradbroke Islandat(6)CanalpinCk
(afterDowling, 1986).
XEROMYSMYOIBESOF NORTH STRADBROKE ISLAND 343
[3] Avicenniamarina varaustralasica Tallopen-shrublandandTallshrubland
[4] Avicenniamarina varaustralasica Open-scrubandClosedscrub
[5] Avicenniamarina varaustralasica Lowopen-woodland, LowwoodlandandWoodland
[7] Avicenniamarina varaustralasica Lowopen-forestandOpenforest
[9] Aegicerascomiculatum Lowopen-shrubtand,LowshrublandandOpen-heath
[11]Aegicerascomiculatum Tallshrubland, Open-scrubandClosed-scrub
[15] Ceriopstagatvaraustralis Tallopen-shrubland,Tallshrubland.Open-scruband Closed-scrub
[rjLandsubjecttotidalinundationcomprisingsaltwatercouchandorsamphireflatsormarineclays
It]Landsubjecttopermanentorseasonalinundation
FIG. 6. Sitesand vegetation types surveyed forXerornysmyoides on North Stradbroke Island at (7) Stockyard
(afterDowling, 1986).
344 MEMOIRS OFTHEQUEENSLAND MUSEUM
TABLE I. North Siradbroke Island sites surveyed, vegetation types and trappingresults forXeromysmyoides.
Site Latitude/Longitudeblock Vegetationtype(s) TrapNights Captures Recaptures Individuals
1 ChiggilChiggil 27o25'00-10"S153°26'13-19"E 3.5 64 8 1 7
2RainbowChannel 27°27'06"-28'00"S t53°25*22-49"E 2,3,5,7,18 1153 128 48 80
3MyoraSprings 27D28,10-21"S153°25'I8-26"E 4.5 25 6 6
4TwoMile 27°28'43-53"S153°24-3i-49"E 7 25 1 1
>Deanhilla 27°30'48" 31 09"S 153"24*41-47 E 5 45 8 1 7
6CanalpinCk 27°36'08-44"S 153°24'22-42"E 3,4,5.7 70 6 6
7Stockyard 27°43,28-46"S 153°24*17-30"E 4.5.9.15 50 5 1 4
Totals 1432 162 51 ill
in somecasesbehaved in an ataxic mannerwhen transmitter life was often unpredictable, animals
releasedthe followingevening.Ratsusedinradio were tracked soon aftercaptureandthereafterfor
tracking were fitted with aTitley (Ballina, NSW) one or two nights. Length oftracking period was
'Microlile', two-stage transmittereitherattached always dependent on the time of capture mea-
toacable-tie collarwith aprotruding 15cmwhip sured against height and time of the night high
antenna orepoxy-potted into a small rectangular tide. As animals usually stayed in their nest until
tablet (length 17.7mm, breadth 9.3mm, height the tide receded, up to four hours of telemetry
6.8mm) with a protruding 18.5cm antenna. The might be lost in a night to a high tide. All X.
ventral surface ofthe epoxy disc transmitter was myoidesstudiedon NorthStradbrokewerenoctur-
glued to a 20mm x 10mm piece ofcloth which nal. Tracking was continuous and direct observa-
was in turn glued to the animal's rump (Selley's tion was used to maximise return of ecological
Supa Glue) after a square of fur approximating information. Places visited on a rat's traversed
thedimensionsoftheclothhadfirstbeencropped route were marked with flagging tape complete
closetotherat'sskin.Theshorthairthatremained with time of recording and subsequently sur-
provided a bonding surface for the glue on the veyed during the day.
transmitter cloth and long hair surrounding the The pattern of habitat use by X. myoides was
positioned disc was then glued over the dorsal not uniform throughoutitsentire homerange and
surface of the cloth and transmitter. Given the a percentage usage pattern defined by the 95th
small size ofthe animal and the saline nature of and 65th percent probability isopleth proved a
itsenvironment,batterysize(hencelongevityand most desirable method forestimating home ranges
range) had to be traded against weight of the and core areas. Swihart & Slade (1985) have
waterproofing agent protecting the unit. Total commented that direct observation through con-
weights of transmitter packages were approx- tinuous tracking may lead to an underestimation
imately 1.8g (collar) and 1.3g (glue-on). As re- ofhome rangesize through lossofindependence
capture of individual rats was unreliable, collars of fixes. To test this, ten-minute fixes were ex-
were abandoned early in the study in favour of tracted from examination of each of the nine
glue-on units that could be removed more easily routes plotted through time. Home range esti-
by the rodents. Adrawback associated with glue- mates arrived at through this method greatly un-
on units was the abilityofratstotwist aroundand derestimated observed patterns of usage and
bite the transmitter package. Any intrusion of failed to demonstrate a picture of overlap. Fixes
saltwaterintothe unitresulted inelectrolysis that taken for each animal followed are outlined in
renderedit inoperable.Glue-onunitsusuallyonly Table 3. Estimates ofhome range area were gen-
lasted on an individual for two nights. A 2000 erated using the harmonic mean distance mini-
channel kRegal 2000' (Titley) portable receiver mum(HM, seeDixon &Chapman, 1980)andthe
operatingon the 150.000-151.999mHzband,and minimum convex polygon (MCP: Mohr, 1974).
a 2 element hand-held H-frame antenna were The utility and appropriateness of the HM for
used to locate animals. describing home ranges of small, fast-moving
mammals wasdemonstrated by Quin et al. (1992).
HOME RANGE DETERMINATION. Home Estimates were generated with the RANGES 4m
range estimates were determined between May computerpackage.
1992and March 1993 forfouradult females, four
adult males and one sub-adult male (Table 3). SPOTLIGHTING, DIET ASSESSMENT AND
Because visits to the area were irregular and NEST ENDOSCOPY. Radio-tagged animals
XEROMYSMYOIDESOFNORTH STRADBROKE ISLAND 345
N Mean OR SD CV TABLE 2. Measurements, and incidence of dorsal
spottingforXeromysmyoidesfromNorthStradbroke
Head-Bodv Length Is.N=number,OR=observedrange,SD=standardde-
adult 42M 102.4 86.4-123.3 8.32 8.12 viation,CV=coefficientofvariation. Lengthsin mm.
(>35g) 26F 98.3 83.1-119.8 8.84 8.99
sub-adult 7M 91.6 83.4-99.0 5.17 5.64 were observed with 'Mag-Lite' (Mag Instru-
(28-35g) 23F 88.6 76.0-103.5 6.03 6.80 ments, Ontario, Calif) torches. The expanding
juvenile 5M 81.1 70.2-94.1 7.75 9.56 beamofthesetorchesgreatly facilitateddetection
«28*) 7F 81 9 62.3-94.8 10.27 12.54 ofrats moving among mangrove roots. Atotal of
Tail-VentL-ength 57 hours was spent observing wild X. myoides
adull 43M 81.8 69.3-90.0 5.32 6.50 (Table3). Ratsweremoredifficulttolocateinside
26F 80.0 74.4-87.5 3.90 4.87 densely vegetated communities (e.g., Rainbow
7M 76.0 67.8-91.0 7.56 9.94 Channel),butinareasoflowvegetationcomplex-
sub-adult 23F 73.8 67.7-84.2 4.16 5.64 ity (e.g., Canalpin Creek, Chiggil Chiggil) the
juvenile 5M 63.8 59.0-70.8 4.48 7.02 white bellies of running rats were conspicuous.
Animals were generally silent and in torchlight
7F hi 7 59,7-74.1 4.30 6.35 the eyes reflected poorly (dull mauve),The diet
HindFool .ength(su1 wasassessed by directlyobserving (with binocu-
adult 43M 23.2 21.6-24.6 0.75 3.23 lars) radio-tagged rats while they fed, and by the
26F 22.1 21.0-24.1 0.70 3.17 analysis of middens attributed to the rats. Rats
sub-adult 7M 22.9 22.0-24.0 0.68 2.97 were interrupted soon afterthey began to eat soft
23F 21.7 20.9-22.8 0.54 2.49 preyand thefoodremnantswerepiratedforiden-
juvenile 5M 20.6 19.9-22.0 78 3.79 tification. Crustacean prey were identified from
7] 21.0 19.7-21 7 M 3.52 skeletal fragments collected after the meal. Fae-
Ear(fromnotch) cal pellets were sampled from manyanimals, but
adult 42M 12.5 10.5-14.0 0.72 5.76 apart from parasites, their contents consisted
25F 12.5 10.7.14,4 0.79 6.32 mostly of minute fragments of unidentifiable
7M 11.8 11.2-12.3 0.37 3.13 crustacean shell and integument.
sub-adult
23F 12.1 10.1-13.8 0.87 7.19 Non-intrusive observation inside nesting-
juvenile 5M 11.7 10.4-13.1 1.02 8.72 mound tunnels, nest chambers and of nestling
6F 11.8 i0.0-12.8 0.96 8.13 young was facilitated by the use ofanendoscope
Anal-GenitalDistance (Olympus GIF type P2) and cold light supply
adult 42M 17.3 10.8-23.2 3.34 19.31 (Olympus CLE-3) powered by a portable Honda
240Vgenerator. Extensiveconvolutionoftunnels
273MF 174..01 142..15--91.77.3 i1..5425 2100..7718 in nest mounds made it impossible to reach nest
sub-adult chambers ifthe endoscope was inserted through
22F 5.8 3.5-7.0 0.79 13.62
juvenile 5M 11.2 8.0-16.2 2.79 24.91 arenaacthurnaelstecnthraamnbcee.rsHouswienvgera,15itmwma-swipdoessihbollelotwo
7F 6.1 5.4-6.4 0.37 6.06 coring rod (fibreglass fishing rod) pushed and
Weighttg) twisted gently into the roofofthe mound. When
adull 42M 46.6 36.0-59.0 6.04 12.96 a lack ofresistance in the passage ofthe rod was
26F 42.0 36.0-54.0 5.06 12.04 detected, the coring rod was extracted, cleaned
sub-adult 7M 32.0 28.0-35.0 2.39 7.46 out, reinserted, and the flexible endoscope tube
23F 31.5 28.0-35.0 2.20 6.98 then introduced and an examination of the area
juvenile 5M 21.8 18.0-26.0 3.12 14.31 made.
7F 24.1 18.0-27.0 3.36 13.94
Spotting N With Without STUDYSITE AND HABITAT. At each site sur-
adult 43M 40 3 veyed forX. myoides, all mangrove species were
26F 25 1 noted and the vegetation was classified visually
7M 5 2 according to density and height into one of the
sub-adult community types of Dowling (1986) described
23F 15 8
juvenile 5M 5 below.
North Stradbroke Island, which forms the
7F 4 3
major part of the eastern boundary of Moreton
Bay, lies 40km east of Brisbane. The island is
triangular in shape, 36km long from north to
346 MEMOIRS OFTHEQUEENSLAND ML'SF.LM
south and about l&Skffl in area (Fig 2: Phssi- p:>ur drainage, but frequent tidal inundation, A,
ography. geology, soils, climate, hydrology and mannaformsa low spindlytree. Where freshwa-
plant communities of this humid subtropical is- ter seepage occurs this species tends to form
land arc broadlv- outlined in Stevens & Monroe stunted, round, leafy hushes. Death o\ Avicenma
(1975). Clifford * Spechi \1979).Covacevieh & marina occurs with waterlogging, ponding of
DNuornbhidgSctraIdIb9trioke a[ngdlanCdo'lsemweasntecrinalm.an(g1r98o4v)e pwnaeteurmaatnodphosirlelsa.lioTnhleeasdtirnugctutroalthfeorcmovseroifng4wof
communities hieing the shelter of Mure'.on Bay cennia marina encountered during this study
haraetcrised by three ubiquitous and d< ranged from Low open-shrubland, Low shrub-
nanl plant species [Avicenma marina,
landandOpen-heath(mapping unit2),Tallopen-
i/a tryios&sr\$Bru&uleragymnartii shrubland and Tall shrubland (mapping unit 3),
of wide ecological amplitude, i.e.. tolerant of a Low open-woodland, Low woodlandand Wood
wide range of salinity and temperature regimes land (mapping unit 5) and Low open-forest and
i Muni etal . 1982),Tredrainage basin supporting Open-forest (mapping unit 7) (Fig. 7; sec Cowl-
themangrovecommunitiesis in arelatival;, low- ing, 1979. 1986 fordefinitions anddesenpnuns).
rainfal] range (Dunwich annual precipitation Throughout Moreton Bay. Rhizophora xtytom
I602nunjhut withan intermediate to lowrun-oft
•.*lT>eiem (ratio o( run-off (o rainfall, 0.2 "5) occurs eitheras solitary trees, in clumps o(three
which, given the island's extensive swamps, to live, or Fa pure stands ofdensely-packedtrees.
Qveift« geiaiionandsandy sub- It may also occur in association with other man
strate,allowsconsiderableretentionofwaterwith speciesas a large, single-stemmedshrubor
mnrc regulated anil sustained release tothedrain- small tree toward the lower tidal limits or occa-
age systems (Hulchings & Sacngcr, 1987). How- sionally in averynarrow/onebehindtheseaward
ever, in backing onto Melaleuca qumquvnervta fringe ofA. marina. Freshwater from Melaleuca
swamps and other poorly drained areas, as com swamps is thought to smni the development of
monly is the case, the full development oi many this Species (DoWlin.fi, 1986). Indie study areaR.
mangroves /.ones is impeded In DOWpariSOi 10 >Stt grew m both isolated clumps and in ih\ k
those 2UI16S abutting better drained and drier belts Trees growing in clumps were represented
areas (Howling, 1979), by individuals of different heights (I-4m) aitd
The mangrove communities most enmmonly age Bells of this species were found behind the
seaward ofAvkenniamarinaandextended
associated with this Study (Table I) comprised 11Ingfi
Ayicenrtja marina var. ausrralasica, Rhizophora to the landwardedge. Here the trunks were more
stylosa and Bruguierti gytnttattfitza. Two other erect and unbranched. the prop and stilt roots
stpaegcaifevsi,KAaeu$s:icrta'trias\wceorrenimcourhetmctoimmaonndlyC#rreiporpei- d(iadnglneodt tsoprIemadabloatveeratlhley.grStoruuncdtuarnadl tfhoerbmrsano\c'heRs
sented toward the southern end of the island. stylosaencounteredduringthisstudyconsistedof
Species descriptions and community composi- Tall shrubland. Open-scrub and Closed-scrub
tions for this group in Moreton Ray can be fOUftd (Fig. 8; mapping unit 18. Dowling, 1986),
in Dowling 1986), Irom whichonly broad char- Bruguieragymnorrhizaoccurs in Moreton Bay
I*
acteristics relevant to this study mc summarised asscattered plantsorsmall clumpsof 10-15trees
below. on the most landward fringes It is found on hard
Avicenma marina var. austraiasica, the most consolidated muds or peaty clays and is most
common and widespread species found in common in areasoffreshwaterseepage from the
Morclon Bay. occurs in any pan ofthe intertidal supralittoral zone. In the study area it did not
eithtt as a pure stand or ituxed with other occur in communities, but as solitary trees up to
species, bul usually as an emergent, Ic is also the 4m or small clumps (two to five trees).
mean vaj abte^pectesin MorttonBay,betngiw- Aegiceras comiculattan (2m tall) occurred ad-
rcscntcd as large, well-developed trees from 10- jacent tothe reed /oneon thelandwardsideofthe
l tn (Of more) tall, or as small spreading shrubs I "anulpni Creekand Stockyard sites. Tin
only 0.5m tall when fully developed. Its growth grows on firm muds which have a shallow layer
is tallest and most vigorous when this Species o\' soft mud on top. It grows on poorly-drained
Stands 91 die extreme seaward edge in well soils that are shallowlv inundated by most high
drained soils that are inundated by all high tides. tides, Structural EWTOS encountered included
At(heuppertida! limitsitsgrowtbislessvigorous Low open ShruH I Open-heath (mapping
and it usually occursas a sii Lib. in arcasof unit9),