experimental tests of food limitation larsen et al. 1997. j. mamm. 78:192-203 becker et al. 1998....
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Experimental tests of
food limitation
Larsen et al. 1997. J. Mamm. 78:192-203
Becker et al. 1998. Oikos 81:81-92
Boutin & Larsen 1993 J.Anim.Ecol. 78:192-203
• Individual as the experimental unit
The effects of food supplementation on winter survival…
1989 1990
-C C +C +S C +C +S
Win
ter
Sur
viva
l
0
20
40
60
80
100
p=0.07 p=0.22
…body mass
1989 1990
-C C +C +S C +C +S
Pre
par
tum
Ma
ss (
g)
0
50
100
150
200
250
300
p=0.79 p=0.27
…parturition date
1988 1990
-C C +C +S C +C +S
Par
turit
ion
Dat
e
Apr 2
Apr 12
Apr 22
May 2
May 12
May 22
Jun 1
p=0.003 p=0.73
ReproductiveEnergetics
• Natural and experimental variation in litter size
• Short-term energetic and behavioural consequences
• Long-term life history consequences
Humphries & Boutin 2000 Ecology 81:2867-77
Humphries & Boutin. 1996. J. Anim. Ecol. 65:332-338
Humphries & Boutin 1999 Can. J. Zool. 77:171-73
1994 1995
Aug Con Aug Con
Gro
wth
Rat
e(g
ram
s pe
r da
y)
0.0
0.5
1.0
1.5
2.0
2.5
Juvenile growth
Treatment p=0.009 Year p<0.001
1994 1995
Aug Con Aug Con
% T
ime
For
agin
g
0
10
20
30
40
50
Maternal behaviour
Treatment p=0.54 Year p<0.001
6 7 8 9 10 11 12 13
Dai
ly E
nerg
y E
xpen
ditu
re(k
J / g
/ da
y)
1.20
1.35
1.50
1.65
1.80
1.95
2.10
2.25
Lower Critical Temperature - Ambient Temperature (oC)
Augmented
Control
Donor
Maternal expenditure
Treatment p=0.001 Temperature p<0.001
Ave
rage
Litt
er S
ize
0
1
2
3
4
Gro
wth
Rat
e (g
/day
)
0.0
0.5
1.0
1.5
2.0
Year
1989 1990 1991 1992 1993 1994 1995 1996 1997
Spr
uce
Con
e In
dex
0
50
100
150
200
Litte
r S
urvi
val (
%)
0
20
40
60
80
100