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| Publications of Rebecca Rimbach :chronological alphabetical combined listing:
%% Journal Articles
@article{fds358342,
Author = {Rimbach, R and Amireh, A and Allen, A and Hare, B and Guarino, E and Kaufman, C and Salomons, H and Pontzer, H},
Title = {Total energy expenditure of bottlenose dolphins (Tursiops
truncatus) of different ages.},
Journal = {The Journal of Experimental Biology},
Volume = {224},
Number = {15},
Year = {2021},
Month = {August},
url = {http://dx.doi.org/10.1242/jeb.242218},
Abstract = {Marine mammals are thought to have an energetically
expensive lifestyle because endothermy is costly in marine
environments. However, measurements of total energy
expenditure (TEE; kcal day-1) are available only for a
limited number of marine mammals, because large body size
and inaccessible habitats make TEE measurements expensive
and difficult to obtain for many taxa. We measured TEE in 10
adult common bottlenose dolphins (Tursiops truncatus) living
in natural seawater lagoons at two facilities (Dolphin
Research Center and Dolphin Quest) using the doubly labeled
water method. We assessed the relative effects of body mass,
age and physical activity on TEE. We also examined whether
TEE of bottlenose dolphins, and more generally of marine
mammals, differs from that expected for their body mass
compared with other eutherian mammals, using phylogenetic
least squares (PGLS) regressions. There were no differences
in body mass or TEE (unadjusted TEE and TEE adjusted for
fat-free mass) between dolphins from the two facilities. Our
results show that adjusted TEE decreased and fat mass
increased with age. Different measures of activity were not
related to age, body fat or adjusted TEE. Both PGLS and the
non-phylogenetic linear regression indicate that marine
mammals have an elevated TEE compared with that of
terrestrial mammals. However, bottlenose dolphins expended
17.1% less energy than other marine mammals of similar body
mass. The two oldest dolphins (>40 years) showed a lower
TEE, similar to the decline in TEE seen in older humans. To
our knowledge, this is the first study to show an
age-related metabolic decline in a large non-human
mammal.},
Doi = {10.1242/jeb.242218},
Key = {fds358342}
}
@article{fds357553,
Author = {Rimbach, R and Amireh, A and Allen, A and Hare, B and Guarino, E and Kaufman, C and Salomons, H and Pontzer, H},
Title = {Total energy expenditure of bottlenose dolphins (Tursiops
truncatus) of different ages.},
Journal = {The Journal of Experimental Biology},
Year = {2021},
Month = {July},
url = {http://dx.doi.org/10.1242/jeb.242218},
Abstract = {Marine mammals are thought to have an energetically
expensive lifestyle because endothermy is costly in marine
environments. However, measurements of total energy
expenditure (TEE; kcal/day) are available only for a limited
number of marine mammals, because large body size and
inaccessible habitats make TEE measurements expensive and
difficult for many taxa. We measured TEE in 10 adult common
bottlenose dolphins (Tursiops truncatus) living in natural
seawater lagoons at two facilities (Dolphin Research Center
and Dolphin Quest) using the doubly labeled water method. We
assessed the relative effects of body mass, age, and
physical activity on TEE. We also examined whether TEE of
bottlenose dolphins, and more generally marine mammals,
differs from that expected for their body mass compared to
other eutherian mammals, using phylogenetic least squares
(PGLS) regressions. There were no differences in body mass
or TEE (unadjusted TEE and TEE adjusted for fat free mass
(FFM)) between dolphins from both facilities. Our results
show that Adjusted TEE decreased and fat mass (FM) increased
with age. Different measures of activity were not related to
age, body fat or Adjusted TEE. Both PGLS and the
non-phylogenetic linear regression indicate that marine
mammals have an elevated TEE compared to terrestrial
mammals. However, bottlenose dolphins expended 17.1% less
energy than other marine mammals of similar body mass. The
two oldest dolphins (>40 years) showed a lower TEE, similar
to the decline in TEE seen in older humans. To our
knowledge, this is the first study to show an age-related
metabolic decline in a large non-human mammal.},
Doi = {10.1242/jeb.242218},
Key = {fds357553}
}
@article{fds356123,
Author = {Rimbach, R and Pillay, N and Schradin, C},
Title = {Prolonged growth during the food-restricted dry season in a
small African mammal},
Journal = {Journal of Mammalogy},
Volume = {102},
Number = {1},
Pages = {296-307},
Publisher = {Oxford University Press (OUP)},
Year = {2021},
Month = {February},
url = {http://dx.doi.org/10.1093/jmammal/gyaa169},
Abstract = {Studying how different environmental parameters, such as
resource availability and ambient temperature, affect growth
rates aids to understand the evolution of different growth
strategies. Low levels of food availability restrict growth,
and high ambient temperature can constrain growth via
trade-offs between body temperature maintenance and heat
produced during digestion. We studied growth of African
striped mice (Rhabdomys pumilio), a small mammal living in a
seasonally arid habitat. Striped mice are born during spring
with high food availability and low ambient temperature, and
typically enter the food-restricted dry season before
reaching adulthood. We predicted low food availability and
high ambient temperature would negatively affect growth. We
therefore expected an extended period of slow growth during
the long dry season. We repeatedly measured body length of
369 free-living individuals, examined how ambient
temperature and food availability influenced growth rate,
and seasonal changes in growth rate. In addition, we
investigated whether mice (N = 27) born in summer (atypical
breeding season) have slower growth rates than those born in
spring. Growth rate increased with increasing food
availability and decreased with increasing ambient
temperature. Individuals born in summer grew slower than
those born in spring. Sexes reached asymptotic body length
at 258 days (females) and 285 days (males), which is an
unusually long growth period compared with other small
rodents. As most striped mice live for less than 1 year,
this period encompasses the entire life for most
individuals, but stops at old age, which could indicate
senescence. Our results demonstrate a positive influence of
food availability on growth, a relationship mediated by
ambient temperature. We conclude that striped mice enter the
food-restricted dry season before postnatal growth is
terminated, and early exposure to harsh environmental
conditions during the long dry season likely explains the
prolonged growth period in striped mice.},
Doi = {10.1093/jmammal/gyaa169},
Key = {fds356123}
}
@article{fds353247,
Author = {Pontzer, H and Rimbach, R and Paltan, J and Ivory, EL and Kendall,
CJ},
Title = {Air temperature and diet influence body composition and
water turnover in zoo-living African elephants (Loxodonta
africana): Water turnover in African elephants},
Journal = {Royal Society Open Science},
Volume = {7},
Number = {11},
Pages = {201155},
Publisher = {The Royal Society},
Year = {2020},
Month = {November},
url = {http://dx.doi.org/10.1098/rsos.201155rsos201155},
Abstract = {African elephants, the largest land animal, face particular
physiological challenges in captivity and the wild. Captive
elephants can become over- or under-conditioned with
inadequate exercise and diet management. Few studies have
quantified body composition or water turnover in elephants,
and none to date have examined longitudinal responses to
changes in diet or air temperature. Using the stable isotope
deuterium oxide (2 H 2 O), we investigated changes in body
mass, estimated fat-free mass (FFM, including fat-free gut
content) and body fat in response to a multi-year
intervention that reduced dietary energy density for adult
African elephants housed at the North Carolina Zoo. We also
examined the relationship between air temperature and water
turnover. Deuterium dilution and depletion rates were
assayed via blood samples and used to calculate body
composition and water turnover in two male and three female
African elephants at six intervals over a 3-year period.
Within the first year after the dietary intervention, there
was an increase in overall body mass, a reduction in body
fat percentage and an increase in FFM. However, final values
of both body fat percentage and FFM were similar to initial
values. Water turnover (males: 359 ± 9 l d -1; females: 241
± 28 l d -1) was consistent with the allometric scaling of
water use in other terrestrial mammals. Water turnover
increased with outdoor air temperature. Our study highlights
the physiological water dependence of elephants and shows
that individuals have to drink every 2-3 days to avoid
critical water loss of approximately 10% body mass in hot
conditions.},
Doi = {10.1098/rsos.201155rsos201155},
Key = {fds353247}
}
@article{fds347125,
Author = {Rimbach, R and Blanc, S and Zahariev, A and Robin, J-P and Pillay, N and Schradin, C},
Title = {Fat content of striped mice decreases during the breeding
season but not during the food-restricted dry
season.},
Journal = {The Journal of Experimental Biology},
Volume = {222},
Number = {Pt 24},
Year = {2019},
Month = {December},
url = {http://dx.doi.org/10.1242/jeb.208504},
Abstract = {Individuals that are capable of accumulating appropriate fat
stores are assumed to have selective advantages when food
becomes scarce. Similarly to species from temperate zones,
some species inhabiting arid areas accumulate fat stores
prior to periods of food limitation. Yet, we have little
knowledge concerning seasonal variation in body composition
and the relationship between fat store size and
disappearance risk in species from arid habitats. Using the
water dilution method, we examined the body composition of
African striped mice (Rhabdomys pumilio) living in a
seasonal habitat with a long food-restricted dry season. We
tested for seasonal changes in body composition (N=159
measurements of 113 individuals) and whether dry season
survival was related to fat mass (N=66 individuals). Fat
stores were similar in size at the onset and the end of the
dry season, but surprisingly smaller at the onset of the
moist breeding season. Fat stores showed a negative
relationship with food availability. Individual variation in
fat stores was not associated with disappearance risk, but
there was a positive association of disappearance risk with
body mass. Increased disappearance risk of heavy individuals
suggests elevated dispersal rates in competitive
individuals. This study suggests that non-breeding
philopatric striped mice do not accumulate large fat stores
prior to the food-limited dry season but that they might
mobilize fat stores at the onset of the breeding season to
satisfy the energetic demands of reproduction and/or to
decrease costs associated with larger fat stores, such as
increased predation risk.},
Doi = {10.1242/jeb.208504},
Key = {fds347125}
}
@article{fds346667,
Author = {Rimbach, R and Blanc, S and Zahariev, A and Pillay, N and Schradin,
C},
Title = {Daily energy expenditure of males following alternative
reproductive tactics: Solitary roamers spend more energy
than group-living males.},
Journal = {Physiology & Behavior},
Volume = {199},
Pages = {359-365},
Year = {2019},
Month = {February},
url = {http://dx.doi.org/10.1016/j.physbeh.2018.12.003},
Abstract = {In many species, males follow alternative reproductive
tactics (ARTs), where one tactic (called bourgeois) has much
higher reproductive success than alternative tactics
followed by males with lower competitive ability. The extent
to which ARTs differ in energetic costs is unknown, but it
is important to understand the fitness payoffs of ARTs. We
studied male African striped mice (Rhabdomys pumilio) which
follow one of three ARTs: heavy bourgeois males defend
harems of females and have 10 times higher reproductive
success than smaller roamers, which have ten times higher
reproductive success than philopatric males, which remain in
their natal group and are the smallest males. Bourgeois and
philopatric males live in social groups that defend one
territory, while roamers are solitary and roam over larger
areas. We predicted that roamers will face higher energetic
costs compared to group-living males because they do not
gain thermoregulatory benefits of huddling in groups and
might travel larger distances as they have larger home
ranges. We measured daily energy expenditure (DEE) of 30
males, resting metabolic rate (RMR) of 79 males, travel
distances and daily ranges of 31 males and changes in body
mass of 51 males. Roamers had higher DEE and higher RMR than
both types of group-living males. Philopatric males had
shorter travel distances and smaller daily ranges than both
roamers and bourgeois males, which did not differ from each
other. This indicates that the higher DEE of roamers
compared to bourgeois males cannot be explained by larger
travel distances. Philopatrics gained body mass faster than
bourgeois males and roamers, thereby increasing their
competitive ability and thus the probability of later
switching to a tactic of higher reproductive success. Our
results suggest that roamers suffer energetic costs that
might reduce their ability of gaining body mass and thus the
likelihood of switching to the bourgeois tactic, indicating
evolutionary trade-offs between investing energy into
roaming versus gaining body mass.},
Doi = {10.1016/j.physbeh.2018.12.003},
Key = {fds346667}
}
@article{fds346668,
Author = {Schradin, C and Vuarin, P and Rimbach, R},
Title = {The neoteny-helper hypothesis: When to expect and when not
to expect endocrine mechanisms to regulate allo-parental
care?},
Journal = {Physiology & Behavior},
Volume = {193},
Number = {Pt A},
Pages = {127-134},
Year = {2018},
Month = {September},
url = {http://dx.doi.org/10.1016/j.physbeh.2017.12.008},
Abstract = {Family groups with helpers occur in several species of fish,
birds and mammals. In such cooperatively breeding species
all group members help with raising the offspring, i.e.
parents and offspring from previous litters. While the
ecological reasons and ultimate consequences of
allo-parental care have been studied in detail, we know
little about its physiological regulation. We propose three
alternative hypotheses for the endocrine regulation of
allo-parental care. 1. The neoteny-helper hypothesis
predicts that helpers that did not undergo adolescence yet
show helping behavior without any endocrine mechanisms
activating it, as helping is the default response towards
infant stimuli. The endocrine changes during adolescence
would then deactivate helping behavior. 2. The parent-helper
hypothesis predicts that helpers undergo the same endocrine
changes as parents (increased prolactin and corticosterone
levels; decreased testosterone in males but increased
estrogen in females). We predict that this hypothesis is
especially important in post-adolescent helpers. 3. The
helper-specific hypothesis predicts that there are specific
endocrine mechanisms that only exist in helpers but not in
breeders. We review evidence for these three hypotheses in
23 species of fish, birds, and mammals. We found no evidence
for the helper-specific hypothesis but for both other
hypotheses. As predicted, this depended on whether helpers
were pre- or post-adolescent, but information on whether or
not helpers underwent adolescence was often missing. Thus,
future studies should investigate whether or not helpers
have reached sexual maturity, differentiate between pre- and
post-adolescent helpers, and study behavioral changes in
helping behavior during adolescence. We conclude that the
neurobiological circuits in the brain necessary for
allo-parental care might often be the default stage in
helpers from cooperative breeding species, which might be
deactivated by specific endocrine mechanisms during
adolescence, and then would need reactivation for
allo-parental and parental care.},
Doi = {10.1016/j.physbeh.2017.12.008},
Key = {fds346668}
}
@article{fds346669,
Author = {Rimbach, R and Blanc, S and Zahariev, A and Gatta, M and Pillay, N and Schradin, C},
Title = {Seasonal variation in energy expenditure in a rodent
inhabiting a winter-rainfall desert.},
Journal = {Journal of Comparative Physiology. B, Biochemical, Systemic,
and Environmental Physiology},
Volume = {188},
Number = {5},
Pages = {877-888},
Year = {2018},
Month = {September},
url = {http://dx.doi.org/10.1007/s00360-018-1168-z},
Abstract = {Animals that spend more energy than they obtain risk
entering allostatic overload, reducing survival and fitness.
They are predicted to adjust their daily energy expenditure
(DEE) during periods of food scarcity. Adjustments of DEE to
changes in food availability have been well-studied in
species in temperate zones during winter, but less so in
species enduring seasonal droughts. Likely mechanisms
regulating DEE involve adjustments of activity and
maintenance metabolism. Species that experience seasonal
droughts and changes in food availability, like the African
striped mouse (Rhabdomys pumilio), are appropriate model
organisms to study the regulation of seasonal changes of
DEE. We quantified DEE using the 'doubly labelled water'
method, measured resting metabolic rate (RMR), and
concomitantly determined activity levels using all-day focal
observations of 69 free-living striped mice in the cold
moist season with high food availability and the hot dry
season with low food availability. Striped mice decreased
their DEE in the food scarce dry season using multiple
mechanisms, especially reductions in RMR, and reduced
overall physical activity. This was further facilitated
passively by reduced thermoregulatory costs. Our study
demonstrates that animals reduce DEE via active and passive
mechanisms in food-restricted environments, and highlights
that several environmental factors should be considered
simultaneously when aiming to understand how animals cope
with harsh environments.},
Doi = {10.1007/s00360-018-1168-z},
Key = {fds346669}
}
@article{fds346670,
Author = {Pillay, N and Rimbach, R},
Title = {Protein deficiency decreases stereotypic behavior frequency
and prevalence and activity in the striped mouse Rhabdomys
dilectus chakae.},
Journal = {Developmental Psychobiology},
Volume = {60},
Number = {2},
Pages = {194-201},
Year = {2018},
Month = {March},
url = {http://dx.doi.org/10.1002/dev.21587},
Abstract = {Diverse motivational triggers, including diet, elicit
stereotypic behavior. We investigated whether diets
comprised of different protein levels but similar levels of
energy were associated with the occurrence of locomotor
stereotypies in the striped mouse Rhabdomys dilectus chakae.
In a first experiment, 20 stereotypic and 20 non-stereotypic
(10 subjects per sex and per group) juvenile (40 days old)
subjects were placed on baseline (BP), high (HP) or low
protein (LP) diet treatments (120 subjects in total). All
subjects initially identified as stereotypic displayed
stereotypic behavior in the BP and HP treatments on Days
60-63 and Days 80-83 compared to 35% and 12.5% of LP
subjects, respectively. Moreover, LP subjects displayed
lower levels of activity and stereotypic behavior than BP
and HP subjects. Those identified as non-stereotypic never
displayed stereotypy. In a second experiment, 48
individuals, bred and reared on LP and whose parents were
stereotypic, were assigned to either HP (13 males, 12
females) or LP (12 males, 11 females) treatments at 50 days
of age for 30 days. Stereotypy was three times less likely
to occur in the LP than the HP treatment, and activity was
greater in LP-HP individuals than LP-LP individuals. In both
experiments, LP individuals had the lowest body mass.
Striped mice adjusted their behaviors in response to dietary
protein levels. Protein deficiency reduced activity and
stereotypic behavior and prevalence, possibly related to an
energy or neurological deficit.},
Doi = {10.1002/dev.21587},
Key = {fds346670}
}
@article{fds346671,
Author = {Rimbach, R and Jäger, J and Pillay, N and Schradin,
C},
Title = {Food Availability Is the Main Driver of Seasonal Changes in
Resting Metabolic Rate in African Striped Mice (Rhabdomys
pumilio).},
Journal = {Physiological and Biochemical Zoology : Pbz},
Volume = {91},
Number = {2},
Pages = {826-833},
Year = {2018},
Month = {March},
url = {http://dx.doi.org/10.1086/696828},
Abstract = {Resting metabolic rate (RMR) influences energy allocation to
survival, growth, and reproduction, and significant seasonal
changes in RMR have been reported. According to one
hypothesis, seasonal changes in RMR are mainly attributable
to seasonal changes in ambient temperature (T<sub>a</sub>)
and food availability. Studies on species from the temperate
zone indicated that food availability is the main driver.
However, whether this is generally true is unknown, because
studies from the tropics and subtropics, where most species
live, are rare. We studied the African striped mouse
(Rhabdomys pumilio) inhabiting a seasonal environment with
hot dry seasons with low food availability and cold moist
seasons with high food availability. Using 603 RMR
measurements of 277 individuals, we investigated the
relative importance of food availability and T<sub>a</sub>
on RMR during selected periods, in which one extrinsic
factor varied while the other factor was relatively
constant. At similar T<sub>a</sub>, residual RMR increased
with increasing levels of food availability. In contrast,
different T<sub>a</sub> did not influence residual RMR at
similar levels of food availability. Thus, our study on a
subtropical species gives support to the hypothesis, derived
from temperate zone species, that food availability mainly
drives seasonal changes in RMR.},
Doi = {10.1086/696828},
Key = {fds346671}
}
@article{fds346672,
Author = {Jäger, J and Schradin, C and Pillay, N and Rimbach,
R},
Title = {Active and explorative individuals are often restless and
excluded from studies measuring resting metabolic rate: Do
alternative metabolic rate measures offer a
solution?},
Journal = {Physiology & Behavior},
Volume = {174},
Pages = {57-66},
Year = {2017},
Month = {May},
url = {http://dx.doi.org/10.1016/j.physbeh.2017.02.037},
Abstract = {It has often been proposed that bolder, more explorative or
more active individuals also have a higher resting metabolic
rate (RMR), indicating metabolic costs of these personality
types. However, such individuals might often be restless and
thus excluded from RMR datasets, leading to a significant
sampling bias. We tested (1) whether such a bias occurs when
animals are measured for a relatively common but short time
period of 3h, and if so, (2) whether alternative measures of
metabolic rate, that allow the incorporation of non-resting
individuals, would reveal associations between metabolism
and personality. For this, we studied free-living
individuals of the African striped mouse (Rhabdomys pumilio)
both during the moist season (N=25 individuals) with high
food availability and the dry season (N=48 individuals) with
low food availability. We assessed variation in the latency
to explore a novel object, and the time spent active and
time spent in the centre of a neutral arena. We examined
links between personality and (i) RMR and (ii) four
alternative metabolic rate (MR) metrics: average MR, highest
MR, lowest MR and span of MR. Twenty-nine percent of the
measured individuals had to be excluded from our RMR study
because they remained restless during respirometry trials.
Striped mice showed a behavioural syndrome where fast
explorers also spent more time in centre and more time
active than slow explorers. Individuals that did not rest
during respirometry trials were faster explorers and in the
moist season, they were also more active and spent more time
in the centre than individuals that rested. We found no
relationship between RMR and the behavioural syndrome, which
might be due to the exclusion of individuals with a certain
behavioural type, leaving a subset of compliant individuals.
In the moist season, we found positive relationships between
the behavioural syndrome and span of MR and lowest MR. In
the dry season, low food availability may mask links between
the behavioural syndrome and alternative MR measures due to
reduced overall activity in striped mice. Our study
demonstrated the importance to consider personality when
measuring RMR and suggests that some alternative MRs may be
useful to examine relationships between metabolism and
personality when it is impossible to measure individuals
over extended time periods.},
Doi = {10.1016/j.physbeh.2017.02.037},
Key = {fds346672}
}
@article{fds346673,
Author = {Rimbach, R and Wastavino, M and Yuen, CH and Pillay, N and Schradin,
C},
Title = {Contrasting activity budgets of alternative reproductive
tactics in male striped mice},
Journal = {Journal of Zoology},
Volume = {301},
Number = {4},
Pages = {280-289},
Year = {2017},
Month = {April},
url = {http://dx.doi.org/10.1111/jzo.12414},
Abstract = {To maximize their fitness, individuals of one sex can
display discrete reproductive phenotypes, called alternative
reproductive tactics (ARTs). Individuals following ARTs show
behavioural variation, which might result in differences in
energy intake and expenditure. However, few studies have
compared activity budgets and non-sexual behaviour of
individuals following ARTs in nature. We studied male
African striped mice Rhabdomys pumilio, which can follow
three ARTs: (1) breeding male of a group of females; (2)
philopatrics remaining in their natal group; or (3) solitary
living roamers. We predicted that each tactic is
characterized by its specific activity budget, representing
alternative energy trade-offs. We conducted focal animal
observations on 70 males following ARTs. Roamers had higher
travelling rates than philopatrics, and breeders had larger
daily range sizes compared to philopatrics but not roamers.
Philopatrics had higher foraging rates than breeders and
showed more socio-positive behaviour than roamers. Breeders
and philopatrics were in their nest more often than roamers,
potentially engaging in social interactions with other group
members. Roamers were chased off more often than breeders,
but the three tactics did not differ concerning rates of
socio-negative behaviour. Overall, philopatrics allocated
their time towards behaviours that would increase body mass
and survival probability, which could improve the
probability to switch to a tactic of higher reproductive
success. In contrast, breeders and roamers allocated their
time towards behaviours that would increase their chances to
mate. In conclusion, following ARTs results in contrasting
activity budgets that reflect the differences in
reproductive behaviours observed between
tactics.},
Doi = {10.1111/jzo.12414},
Key = {fds346673}
}
@article{fds346674,
Author = {Rimbach, R and Pillay, N and Schradin, C},
Title = {Both thyroid hormone levels and resting metabolic rate
decrease in African striped mice when food availability
decreases.},
Journal = {The Journal of Experimental Biology},
Volume = {220},
Number = {Pt 5},
Pages = {837-843},
Year = {2017},
Month = {March},
url = {http://dx.doi.org/10.1242/jeb.151449},
Abstract = {In response to variation in food availability and ambient
temperature (<i>T</i><sub>a</sub>), many animals show
seasonal adaptations in their physiology. Laboratory studies
showed that thyroid hormones are involved in the regulation
of metabolism, and their regulatory function is especially
important when the energy balance of an individual is
compromised. However, little is known about the relationship
between thyroid hormones and metabolism in free-living
animals and animals inhabiting seasonal environments. Here,
we studied seasonal changes in triiodothyronine
(T<sub>3</sub>) levels, resting metabolic rate (RMR) and two
physiological markers of energy balance (blood glucose and
ketone bodies) in 61 free-living African striped mice
(<i>Rhabdomys pumilio</i>) that live in an semi-arid
environment with food shortage during the dry season. We
predicted a positive relationship between T<sub>3</sub>
levels and RMR. Further, we predicted higher T<sub>3</sub>
levels, blood glucose levels and RMR, but lower ketone body
concentrations, during the moist season when food
availability is high compared with summer when food
availability is low. RMR and T<sub>3</sub> levels were
negatively related in the moist season but not in the dry
season. Both RMR and T<sub>3</sub> levels were higher in the
moist than in the dry season, and T<sub>3</sub> levels
increased with increasing food availability. In the dry
season, blood glucose levels were lower but ketone body
concentrations were higher, indicating a change in substrate
use. Seasonal adjustments in RMR and T<sub>3</sub> levels
permit a reduction of energy expenditure when food is
scarce, and reflect an adaptive response to reduced food
availability in the dry season.},
Doi = {10.1242/jeb.151449},
Key = {fds346674}
}
@article{fds346675,
Author = {Rimbach, R and Willigenburg, R and Schoepf, I and Yuen, CH and Pillay,
N and Schradin, C},
Title = {Young But Not Old Adult African Striped Mice Reduce Their
Activity in the Dry Season When Food Availability is
Low},
Journal = {Ethology},
Volume = {122},
Number = {10},
Pages = {828-840},
Year = {2016},
Month = {October},
url = {http://dx.doi.org/10.1111/eth.12527},
Abstract = {An individual′s survival and fitness depend on its ability
to effectively allocate its time between competing
behaviors. Sex, social tactic, season and food availability
are important factors influencing activity budgets. However,
few field studies have tested their influences. The African
striped mouse (Rhabdomys pumilio) lives in highly seasonal
habitats in southern Africa, and individuals can adopt
different social tactics. We investigated seasonal changes
in activity budgets of different tactics and predicted that
individuals will reduce their activity in the non-breeding
season to save energy when food availability is low and that
young non-breeding adults (‘philopatrics’) invest mainly
in activities related to gaining body mass to increase
survival probability. We predicted old adults
(‘breeders’), which bred during the previous breeding
season, to invest mainly in maintenance of their social
status. We conducted 90 focal observations during the
non-breeding season and 73 during the breeding season.
Activity budgets of striped mice were season and tactic
specific, with philopatrics, but not breeders, reducing
activity when food availability was low, possibly to
decrease energy expenditure. Philopatrics of both sexes
foraged and basked more in the breeding season than during
the non-breeding season. Male philopatrics gained body mass
and female philopatrics maintained their body mass in both
seasons. Sex-specific differences occurred during the
breeding season, when female breeders foraged more than male
breeders, while male breeders chased other individuals more
than female breeders. These findings indicate that
individuals adopting different social tactics display
distinct behaviors to fulfill tactic-specific energetic
needs.},
Doi = {10.1111/eth.12527},
Key = {fds346675}
}
@article{fds346676,
Author = {Pillay, N and Rimbach, R and Rymer, T},
Title = {Pre- and postnatal dietary protein deficiency influences
anxiety, memory and social behaviour in the African striped
mouse Rhabdomys dilectus chakae.},
Journal = {Physiology & Behavior},
Volume = {161},
Pages = {38-46},
Year = {2016},
Month = {July},
url = {http://dx.doi.org/10.1016/j.physbeh.2016.04.015},
Abstract = {Dietary protein deficiency influences the behavioural
phenotypes of mammals. We studied whether protein deficiency
during gestation and/or post-weaning heightened anxiety,
reduced memory recall and influenced competitive ability in
the African striped mouse Rhabdomys dilectus chakae. Mice
were subjected to five protein diet treatments, which they
received continuously, or were raised on one diet to weaning
and switched to an alternate diet post-weaning (Day 16): 1)
HP-HP: high protein (24%); first letter pair indicates
maternal diet and the second pair indicates offspring diet
post-weaning; 2) BP-BP: baseline protein (19%); 3) LP-LP:
low protein (10%); 4) HP-LP: switched from high to low
protein diet; and 5) LP-HP: switched from low protein to
high protein diet. From Day 70, when mice were sexually
mature, 20 individuals (10 males, 10 females) per treatment
were subjected to three successive experiments, in which we
tested their anxiety responses in: 1) an open field arena
(time spent in the centre of the open field); 2) novel
object recognition (time spent exploring a novel object);
and 3) social interactions (excluding BP-BP) in age-matched
same-sex dyadic encounters (aggressive, amicable and
avoidance behaviours). LP-LP and LP-HP treatment mice spent
the least amount of time in the centre of the open field,
did not demonstrate object preference compared to the other
treatments, and were the most aggressive in dyadic
encounters. Our study shows that the systemic effects of
protein-deficient diets during early life shapes the
behavioural phenotype in R. d. chakae, possibly through
early organisation of neuro-biological pathways or
competition among littermates.},
Doi = {10.1016/j.physbeh.2016.04.015},
Key = {fds346676}
}
@article{fds346677,
Author = {Rimbach, R and Bisanzio, D and Galvis, N and Link, A and Di Fiore and A and Gillespie, TR},
Title = {Brown spider monkeys (Ateles hybridus): a model for
differentiating the role of social networks and physical
contact on parasite transmission dynamics.},
Journal = {Philosophical Transactions of the Royal Society of London.
Series B, Biological Sciences},
Volume = {370},
Number = {1669},
Year = {2015},
Month = {May},
url = {http://dx.doi.org/10.1098/rstb.2014.0110},
Abstract = {Elevated risk of disease transmission is considered a major
cost of sociality, although empirical evidence supporting
this idea remains scant. Variation in spatial cohesion and
the occurrence of social interactions may have profound
implications for patterns of interindividual parasite
transmission. We used a social network approach to shed
light on the importance of different aspects of group-living
(i.e. within-group associations versus physical contact) on
patterns of parasitism in a neotropical primate, the brown
spider monkey (Ateles hybridus), which exhibits a high
degree of fission-fusion subgrouping. We used daily subgroup
composition records to create a 'proximity' network, and
built a separate 'contact' network using social interactions
involving physical contact. In the proximity network,
connectivity between individuals was homogeneous, whereas
the contact network highlighted high between-individual
variation in the extent to which animals had physical
contact with others, which correlated with an individual's
age and sex. The gastrointestinal parasite species richness
of highly connected individuals was greater than that of
less connected individuals in the contact network, but not
in the proximity network. Our findings suggest that among
brown spider monkeys, physical contact impacts the spread of
several common parasites and supports the idea that pathogen
transmission is one cost associated with social
contact.},
Doi = {10.1098/rstb.2014.0110},
Key = {fds346677}
}
@article{fds346678,
Author = {Nel, K and Rimbach, R and Pillay, N},
Title = {Dietary protein influences the life-history characteristics
across generations in the African striped mouse
Rhabdomys.},
Journal = {Journal of Experimental Zoology. Part A, Ecological Genetics
and Physiology},
Volume = {323},
Number = {2},
Pages = {97-108},
Year = {2015},
Month = {February},
url = {http://dx.doi.org/10.1002/jez.1903},
Abstract = {The level of dietary protein determines the onset of
reproduction, affects offspring growth and maturation, and
hence influences life-history traits and fitness. However,
to date, the long-term life-history consequences of protein
deficiency are not well understood. We studied the
transgenerational effects of different levels of dietary
protein on the life-history and level of maternal behavior
of the striped mouse Rhabdomys dilectus chakae in captivity.
Breeding pairs were assigned to three treatments based on
the percentage of dietary protein: baseline (BP; 19%); high
protein (HP; 24%); and low protein (LP; 10%). Reproductive
output and offspring ontogeny was diminished in the LP
treatment compared to the other treatments.
Transgenerational effects were studied by breeding F2
females raised on the LP or HP diets on the same (HP-HP,
LP-LP) or altered diets (HP-LP, LP-HP). The LP-LP treatment
had no reproductive success, while reproductive capacity in
the remaining treatments was determined mainly by the diet
of mothers at breeding. Pups from protein-restricted females
(LP, HP-LP) showed post-weaning compensatory growth. Timing
of sexual maturity was age-dependent in female and
mass-dependent in male offspring. Females fed low protein
diets during breeding (LP, HP-LP) displayed lower levels of
maternal behavior than females from the other treatments.
This study demonstrates that the level of dietary protein
influences the life-history of R. d. chakae in predictable
ways. The taxon responds to changes in dietary protein at
breeding, largely regardless of its nutrition during
rearing. Such phenotypic flexibility in life-history
parameters allows Rhabdomys to adaptively respond to
unpredictable environmental changes.},
Doi = {10.1002/jez.1903},
Key = {fds346678}
}
@article{fds346679,
Author = {Rimbach, R and Link, A and Montes-Rojas, A and Di Fiore and A and Heistermann, M and Heymann, EW},
Title = {Behavioral and physiological responses to fruit availability
of spider monkeys ranging in a small forest
fragment.},
Journal = {American Journal of Primatology},
Volume = {76},
Number = {11},
Pages = {1049-1061},
Year = {2014},
Month = {November},
url = {http://dx.doi.org/10.1002/ajp.22292},
Abstract = {Numerous animal species currently experience habitat loss
and fragmentation. This might result in behavioral and
dietary adjustments, especially because fruit availability
is frequently reduced in fragments. Food scarcity can result
in elevated physiological stress levels, and chronic stress
often has detrimental effects on individuals. Some animal
species exhibit a high degree of fission-fusion dynamics,
and theory predicts that these species reduce intragroup
feeding competition by modifying their subgroup size
according to resource availability. Until now, however,
there have been few studies on how species with such
fission-fission dynamics adjust their grouping patterns and
social behavior in small fragments or on how food
availability influences their stress levels. We collected
data on fruit availability, feeding behavior, stress hormone
levels (measured through fecal glucocorticoid metabolites
(FGCM)), subgroup size, and aggression for two groups of
brown spider monkeys (Ateles hybridus) in a small forest
fragment in Colombia and examined whether fruit availability
influences these variables. Contrary to our predictions,
spider monkeys ranged in smaller subgroups, had higher FGCM
levels and higher aggression rates when fruit availability
was high compared to when it was low. The atypical grouping
pattern of the study groups seems to be less effective at
mitigating contest competition over food resources than more
typical fission-fusion patterns. Overall, our findings
illustrate that the relationship between resource
availability, grouping patterns, aggression rates, and
stress levels can be more complex than assumed thus far.
Additional studies are needed to investigate the long-term
consequences on the health and persistence of spider monkeys
in fragmented habitats.},
Doi = {10.1002/ajp.22292},
Key = {fds346679}
}
@article{fds346680,
Author = {Rimbach, R and Heymann, EW and Link, A and Heistermann,
M},
Title = {Validation of an enzyme immunoassay for assessing
adrenocortical activity and evaluation of factors that
affect levels of fecal glucocorticoid metabolites in two New
World primates.},
Journal = {General and Comparative Endocrinology},
Volume = {191},
Pages = {13-23},
Year = {2013},
Month = {September},
url = {http://dx.doi.org/10.1016/j.ygcen.2013.05.010},
Abstract = {Non-invasive methods to assess stress hormone output via
fecal glucocorticoid metabolites (FGCMs) have become a
powerful tool in behavioral studies and conservation biology
because they allow exploring the link between behavior, an
animal's socio-ecological environment and its adrenocortical
activity. However, FGCM levels are influenced by numerous
other factors which often confound their interpretation.
Thus, before applying these methods, knowledge on the impact
of these factors is important. In this study we investigated
the effect of (1) time of day, (2) age, (3) sex and (4)
female reproductive state on FGCM levels in brown spider
monkeys (Ateles hybridus) and red howler monkeys (Alouatta
seniculus). Initially, we validated a 11β-hydroxyetiocholanolone
enzyme immunoassay for monitoring the physiological stress
response via fecal analysis in both species. We determined
FGCM levels in fecal samples collected from two and six
groups of wild spider monkeys (n=461 samples) and howler
monkeys (n=166 samples), respectively. Our analyses revealed
a strong effect of time of day on FGCM levels in spider
monkeys, but no effect in howler monkeys. Adults of both
species had significantly higher FGCM levels than subadults.
In neither of the two species we found a sex-effect on FGCM
output. Reproductive condition strongly affected FGCM levels
in female spider monkeys which showed increasing
concentrations with progressing gestation. This was not
investigated in female howler monkeys due to an insufficient
sample size. Our data indicate that the influence of the
tested factors on fecal glucocorticoid metabolite output is
species-specific, and that these variables need to be
considered when interpreting FGCM levels in the
species.},
Doi = {10.1016/j.ygcen.2013.05.010},
Key = {fds346680}
}
@article{fds346681,
Author = {Rimbach, R and Link, A and Heistermann, M and Gómez-Posada, C and Galvis, N and Heymann, EW},
Title = {Effects of logging, hunting, and forest fragment size on
physiological stress levels of two sympatric ateline
primates in Colombia.},
Journal = {Conservation Physiology},
Volume = {1},
Number = {1},
Pages = {cot031},
Year = {2013},
Month = {January},
url = {http://dx.doi.org/10.1093/conphys/cot031},
Abstract = {Habitat fragmentation and anthropogenic disturbances are of
major concern to the conservation of endangered species
because of their potentially negative impact on animal
populations. Both processes can impose physiological stress
(i.e. increased glucocorticoid output) on animals, and
chronically elevated stress levels can have detrimental
effects on the long-term viability of animal populations.
Here, we investigated the effect of fragment size and human
impact (logging and hunting pressure) on glucocorticoid
levels of two sympatric Neotropical primates, the red howler
monkey (Alouatta seniculus) and the critically endangered
brown spider monkey (Ateles hybridus). These two species
have been reported to contrast strongly in their ability to
cope with anthropogenic disturbances. We collected faecal
samples from eight spider monkey groups and 31 howler monkey
groups, living in seven and 10 different forest fragments in
Colombia, respectively. We measured faecal glucocorticoid
metabolite (FGCM) levels in both species using previously
validated methods. Surprisingly, fragment size did not
influence FGCM levels in either species. Spider monkeys
showed elevated FGCMs in fragments with the highest level of
human impact, whereas we did not find this effect in howler
monkeys. This suggests that the two species differ in their
physiological responsiveness to anthropogenic changes,
further emphasizing why brown spider monkeys are at higher
extinction risk than red howler monkeys. If these
anthropogenic disturbances persist in the long term,
elevated FGCM levels can potentially lead to a state of
chronic stress, which might limit the future viability of
populations. We propose that FGCM measurements should be
used as a tool to monitor populations living in disturbed
areas and to assess the success of conservation strategies,
such as corridors connecting forest fragments.},
Doi = {10.1093/conphys/cot031},
Key = {fds346681}
}
@article{fds346682,
Author = {Rimbach, R and Pardo-Martinez, A and Montes-Rojas, A and Di Fiore and A and Link, A},
Title = {Interspecific infanticide and infant-directed aggression by
spider monkeys (Ateles hybridus) in a fragmented forest in
Colombia.},
Journal = {American Journal of Primatology},
Volume = {74},
Number = {11},
Pages = {990-997},
Year = {2012},
Month = {November},
url = {http://dx.doi.org/10.1002/ajp.22052},
Abstract = {Interspecific aggression amongst nonhuman primates is rarely
observed and has been mostly related to scenarios of
resource competition. Interspecific infanticide is even
rarer, and both the ultimate and proximate socio-ecological
factors explaining this behavior are still unclear. We
report two cases of interspecific infanticide and five cases
of interspecific infant-directed aggression occurring in a
well-habituated primate community living in a fragmented
landscape in Colombia. All cases were initiated by male
brown spider monkeys (Ateles hybridus) and were directed
toward infants of either red howler monkeys (Alouatta
seniculus: n = 6 cases) or white-fronted capuchins (Cebus
albifrons: n = 1 case). One individual, a subadult spider
monkey male, was involved in all but one case of
interspecific infanticide or aggression. Other adult spider
monkeys participated in interspecific aggression that did
not escalate into potentially lethal encounters. We suggest
that competition for food resources and space in a primate
community living in high population densities and restricted
to a forest fragment of ca. 65 ha might partly be driving
the observed patterns of interspecific aggression. On the
other hand, the fact that all but one case of interspecific
infanticide and aggression involved the only subadult male
spider monkey suggests this behavior might either be
pathological or constitute a particular case of redirected
aggression. Even if the underlying principles behind
interspecific aggression and infanticide are poorly
understood, they represent an important factor influencing
the demographic trends of the primate community at this
study site.},
Doi = {10.1002/ajp.22052},
Key = {fds346682}
}
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