Annual variation in maternal age and calving date generate cohort effects in moose (Alces alces) body mass.
A general feature of the demography of large ungulates is that many demographic traits are dependent on female body mass at early ages. Thus, identifying the factors affecting body mass variation can give important mechanistic understanding of demographic processes. Here we relate individual variation in autumn and winter body mass of moose calves living at low density on an island in northern Norway to characteristics of their mother, and examine how these relationships are affected by annual variation in population density and climate. Body mass increased with increasing age of their mother, was lower for calves born late in the spring, decreased with litter size and was larger for males than for female calves. No residual effects of variation in density and climate were present after controlling for annual variation in mother age and calving date. The annual variation in adult female age structure and calving date explained a large part (71-75%) of the temporal variation in calf body mass. These results support the hypotheses that (a) body mass of moose calves are affected by qualities associated with mother age (e.g. body condition, calving date); and (b) populations living at low densities are partly buffered against temporal fluctuations in the environment.
Solberg
Erling J
EJ
Norwegian Institute for Nature Research, Tungasletta 2, 7485, Trondheim, Norway.
Heim
Morten
M
Grøtan
Vidar
V
Saether
Bernt-Erik
BE
Garel
Mathieu
M
D000367:Age Factors; D000818:Animals; D001835:Body Weight; D003670:Deer / Q000502:physiology*; D005260:Female; D005843:Geography; D016013:Likelihood Functions; D008423:Maternal Age; D009664:Norway; D011156:Population Density; D012621:Seasons
J Theor Biol. 2007 Jan 21;244(2):308-17
16978654
Trends Ecol Evol. 1999 Sep;14(9):343-348
10441307
Trends Ecol Evol. 1997 Apr;12(4):143-9
21238011
Evolution. 1989 May;43(3):485-503
28568400
Oecologia. 2004 Jan;138(1):135-42
14564502
Anim Behav. 1998 Aug;56(2):301-307
9787020
J Anim Ecol. 1998 Nov;67(6):979-86
26412376
Proc Biol Sci. 2002 Apr 7;269(1492):747-53
11934368
Proc Biol Sci. 1997 Sep 22;264(1386):1317-24
9332016
Proc Biol Sci. 1999 Aug 22;266(1429):1655-61
10501037
Science. 2001 May 25;292(5521):1528-31
11375487
Oecologia. 2001 Aug;128(3):400-405
24549909
J Mammal. 1978 Nov;59(4):857-8
750641
Proc Biol Sci. 2000 Mar 7;267(1442):471-7
10737404
Oecologia. 2001 Apr;127(2):230-238
24577654
Evolution. 2003 Dec;57(12):2879-92
14761065
Ecology. 2006 Mar;87(3):745-58
16602303
J Anim Ecol. 2006 Sep;75(5):1110-8
16922846
Nature. 2004 Jul 1;430(6995):71-5
15229599
Am Nat. 1999 Dec;154(6):730-46
10600616
Science. 1995 Aug 4;269(5224):676-9
17758812
Trends Ecol Evol. 1998 Feb 1;13(2):64-9
21238202