BBC Wildlife - UK (2019-12)

Kangaroo:

John

Wh

tePhotos/Getty;

eggs:

Asta

rScott/A

amy;

fish:

Ke

vn

Atken/VWP

cs/A

amy;

eag

e:Er

cMedard/

naturepl.com; squirrel feeding: Andrew Mason/FLPA; squirrel on trunk: Mark Hamblin/2020VISION/NPL

H

oppingonthehindlegsis a defining

characteristicofthemacropod

marsupials:kangaroos,wallabies,bettongs,

potoroosandtheirkin.Eventreekangaroos

hopwhentheyfindthemselvesonthe

ground.It’sa highlyefficientmodeoftravel

thatemploysthick,stretchytendonstoabsorb

andreleaseenergy,likesprings.Whileother

animals require a huge muscular effort to

jump,macropodsquiteliterallybounce.

Atleastonefamilymemberdoesthings

differently,though.Themuskyrat-kangaroo

boundsaroundQueensland’srainforests

onallfourlimbs,placingitsfrontfeeton

thegroundandbringingbothhindfeetup

simultaneouslytomeetthem.So,eventhis

odditycouldbesaidtohop,albeitmorelikea

rabbit than a macropod.Stuart Blackman

T

itsareprodigiousegg-layers,

routinelyproducingclutchesof 10

to 12 withoccasionalrecordsofupto19.

Thesenumbersareimpressivewhen

comparedtosimilar-sizedspeciessuch

assparrows,whichtypicallylayfiveor

six.Thedifferenceis thattitstendto

produceonlyoneclutcha year,while

sparrowsgetonebroodfledgedthen

keepgoing,sothatthetotalfora year

is similar.Titsliterallyputalltheireggs

inonebasketinApril,takingadvantage

ofthesuperabundanceofcaterpillars.

Sparrows,ontheotherhand,relyona

widerrangeofinvertebratefood,often

workingintoautumntofeedsecond,

third or fourth broods.Amy-Jane Beer

Doallkangaroos hop?

Whydoblueand

greattitslayso

many eggs?

MAMMALS

BRITISH BIRDS

MARINEBIOLOGY

Y

es.Forair-breathingcreatureslike

ourselves,anabilitytoholdone’sbreathis

usefulshouldonefindoneselfsubmerged.But

coffinfish,too,routinelyholdtheirbreathinwater

• foruptofourminutes– eventhoughwater
  is whattheybreathe.Assit-and-waitpredators,
  coffinfishdon’textractoxygenastheyswimalong.
  Instead,theymustactivelyinflateanddeflatetheir
  gillchambers.Thesechambersareunusually
  large,allowingthefishtoprocessa largevolume
  ofwaterinonego,whichmayexplainhowthey
  canaffordtobreathesoinfrequently.Butthere
  couldbemoretoit.Inflationofthegillchambers
  increasesbodyvolumeby 30 percent,whichmay
  servetodeterpredators,inmuchthesameway
  thatpufferfishesappearbigger by swallowing
  seawater.Stuart Blackman

Cananysh

hold its breath?

Confishrespiration

• reallyquite
  breathtaking.

Greattitsgo

largeonthe

laying.

Virtuallyall

kangaroos(here

westerngreys)can

be caught on the hop.

Q&A

84 BBC Wildlife December 2019