10.5061/DRYAD.80GB5MKRJ
Pigeon, Gabriel
0000-0002-9166-8633
Norwegian University of Life Sciences
Albon, Steve
James Hutton Institute
Loe, Leif Egil
Norwegian University of Life Sciences
Bischof, Richard
Norwegian University of Life Sciences
Bonenfant, Christophe
University of Lyon System
Farchhammer, Mads
University Centre in Svalbard
Irvine, Justine
James Hutton Institute
Ropstad, Erik
Norwegian University of Life Sciences
Veiberg, Vebjorn
Norwegian Institute for Nature Research
Stein, Audun
Norwegian Institute for Nature Research
Context dependent fitness costs of reproduction despite stable body mass
costs in an Arctic herbivore
Dryad
dataset
2021
FOS: Biological sciences
The Research Council of Norway
https://ror.org/00epmv149
216051
The Research Council of Norway
https://ror.org/00epmv149
267613
UK Natural 513 Environment Research Council*
GR3/10811
UK Natural 513 Environment Research Council
GR3/10811
2021-09-16T00:00:00Z
2021-09-16T00:00:00Z
en
JAE-2021-00461
494298 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
1. The cost of reproduction on demographic rates is often assumed to
operate through changing body condition. Several studies have found that
reproduction depresses body mass more if the current conditions are
severe, such as high population densities or adverse weather, than under
benign environmental conditions. However, few studies have investigated
the association between the fitness and body mass costs of reproduction.
2. Using 25 years of individual-based capture-recapture data from Svalbard
reindeer (Rangifer tarandus platyrhynchus), we built a novel Bayesian
state-space model that jointly estimated inter-annual change in mass,
annual reproductive success, and survival, while accounting for incomplete
observations. The model allowed us to partition the differential effects
of intrinsic and extrinsic factors on both non-reproductive mass change
and the body mass cost of reproduction and to quantify their consequences
on demographic rates. 3. Contrary to our expectation, the body mass cost
of reproduction (mean = 5.8 kg) varied little between years (CV = 0.08)
whereas the between-year variation in body mass changes, that were
independent of the previous year’s reproductive state, varied
substantially (CV = 0.4) in relation to autumn temperature and the amount
of rain-on-snow in winter. This mass loss led to a cost of reproduction on
the next reproduction, which was amplified by the same environmental
covariates, from a 10% reduction in reproductive success in benign years,
to a 50% reduction in harsh years. The reproductive mass loss also
resulted in a small reduction in survival. 4. Our results show how
demographic costs of reproduction, driven by inter-annual fluctuations in
individual body condition, result from the balance between body mass costs
of reproduction and body mass changes that are independent of previous
reproductive state. We illustrate how a strong context dependent fitness
cost of reproduction can occur, despite a relatively fixed body mass cost
of reproduction. This suggests that female reindeer display a very
conservative energy allocation strategy, either aborting their
reproductive attempt at an early stage or weaning at a relatively constant
cost. Such a strategy might be common in species living in a highly
stochastic food limited environment.
The Svalbard reindeer population in Nordenskiöld Land, Svalbard
(77°50’–78°20’ N, 15°00’–17°30’ E), was studied in and around the valleys
of Reindalen, Semmeldalen and Colesdalen where individual-based monitoring
has been conducted, uninterrupted since 1995 (Albon et al., 2017). Up to
2019 a total of 815 individual females have been caught during late winter
(mostly April; range: mid-March to early May), using a net stretched
between two snowmobiles (Omsjoe et al., 2009). New individuals were marked
mainly in their first year of life (c.10 months of age) using coloured and
numbered plastic ear tags and collars and were hence of known age.
Captured females were weighed to the nearest 0.5 kg and the dataset
includes on average 4 annual body mass measurements per individual (sd =
2.2, range = 1 - 12) over their lifetime yielding a total of 2801 mass
estimates across these individuals. All capture and live animal handling
procedures were performed under licenses from the Norwegian Food
Inspection Authority and its predecessor, the Norwegian National Research
Authority. In summer, surveys were conducted by two or more observers
using binoculars and telescopes, between 24 June and 25 August to assess
the presence or absence of a calf associated with marked females. Average
group size in summer is only 2-3 individuals (Loe et al., 2006)
facilitating assignment of mother-calf pairs. Since Svalbard consists of
open landscapes, animals can be easily spotted and identified at long
distances (>1 km). When a female was observed with a calf at heel
during the summer census, it was classified as a successful reproduction
We quantified ROS as the total rainfall occurring on days with mean
temperatures above 0°C during the months of November to March. We
quantified autumn environmental conditions using October degree-days for
days with average temperature >0°C. ROS and October degree-days
were log transformed. Annual summer environmental conditions were
quantified using mean daily June–July temperature, which strongly
influences peak plant biomass and consequently forage availability (Van
der Wal & Stien, 2014). Also, we investigated the negative effect
of high population size on the cost of reproduction. Population size
estimates were obtained from an integrated population model (Lee et al.,
2015). Population size estimates were detrended prior to the analysis to
account for increasing carrying capacity (Hansen et al., 2019). All
environmental variables were centred and scaled to a standard deviation of
1 to facilitate model convergence and parameter comparisons.
jagsDat.Rdata is a list containing all necessary data, ready to run the
model. Can be imported into R using the load() function. The .csv files
contain the necessary data to re-create the same list but in plain text
format. apr.wt : body mass of females at capture in April (scaled values.
mean=42.51285, sd=12.68977). age: age of female in a given year (=1 the
year of birth) dateCapt: date of capture in April( Jullian day centered at
day 107 and divided by sd (9.6). NAs were then filled with 0). idVar:
vector variables relating to individuals all timing numbers are relative
to the observation matrix (not actual years) first.y: first year
captured last.y : last year to be considered in the analysis
(carcass found and known dead after or before removal (hunting or
culling)) yrbirth: year of birth timeVar: vector variables
with length = number of observation occasion ros: rain on snow
(scale(log(x+1))) oct.dd: October degree days (scale(log(x+1)))
summerTemp: average summer (June-July) temperature (scaled)
dens: density (scaled(detrended)) ageC_calf: vector of
correspondence between age and age class for the probability to have a
calf in august ageC_surv: vector of correspondence between age and
age class for the probability to survive