[dinosaur] Moa population estimates (free pdf) + limb loading in tetrapods + lizard running (free pdf)

Ben Creisler
[email protected]

Some recent non-dino papers:

Free pdf:

A. David M. Latham, M. Cecilia Latham, Janet M. Wilmshurst, David M.
Forsyth, Andrew M. Gormley, Roger P. Pech, George L. W. Perry and Jamie R.
Wood (2019)
A refined model of body mass and population density in flightless birds
reconciles extreme bimodal population estimates for extinct moa.
Ecography 42: 1-2 (advance online publication)
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1111_ecog.04917&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=lEiM1wTBMQLydFGAZ8FBHIUCHxTpkDVecNSA28DGlT8&s=CsAkGh6vV9djtkncunvuDxfYnZpVcMkuCs_9J4mGDzo&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_10.1111_ecog.04917&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=lEiM1wTBMQLydFGAZ8FBHIUCHxTpkDVecNSA28DGlT8&s=_tp04QPYQUq1W2DfnsJc9fv4_pQgrfUh83C_Y-Q-7l4&e= 

Free pdf:

https://urldefense.proofpoint.com/v2/url?u=https-3A__onlinelibrary.wiley.com_doi_pdf_10.1111_ecog.04917&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=lEiM1wTBMQLydFGAZ8FBHIUCHxTpkDVecNSA28DGlT8&s=GxaumUoWOn7tEeSQ7793xgp7aIdoDaSRawIlgWuD-nU&e= 


Flightless birds were once the largest and heaviest terrestrial fauna on
many archipelagos around the world. Robust approaches for estimating their
population parameters are essential for understanding prehistoric insular
ecosystems and extinction processes. Body mass and population density are
negatively related for extant flightless bird species, providing a method
for quantifying densities and population sizes of extinct flightless
species. Here we assemble an updated global data set of body mass and
population densities for extant flightless birds and estimate the
relationship between these variables. We use generalised least squares
models that account for phylogenetic relatedness and incorporate the
effects of limiting factors (e.g. habitat suitability) on population
density. We demonstrate the applicability of this allometric relationship
to extinct species by estimating densities for each of the nine species of
moa (Dinornithiformes) and generating a combined spatially explicit map of
total moa density across New Zealand. To compare our density estimates with
those previously published, we summed individual species' abundances to
generate a mean national density of 2.02–9.66 birds km−2 for low‐ and
high‐density scenarios, respectively. Our results reconcile the extreme
bimodality of previous estimates (< 2 birds km−2 and > 10 birds km−2) and
are comparable to contemporary densities of large herbivorous wild mammals
introduced into New Zealand about 150 yr ago. The revised moa density has
little effect on the harvest rates required to bring about extinction
within 150–200 yr, indicating that rapid extinction was an inevitable
response to human hunting, irrespective of the initial population of moa.

===

Michael C. Granatosky, Eric J. McElroy, Pierre Lemelin, Stephen M. Reilly,
John A. Nyakatura, Emanuel Andrada, Brandon M. Kilbourne, Vivian R. Allen,
Michael T. Butcher, Richard W. Blob & Callum F. Ross (2019)
Variation in limb loading magnitude and timing in tetrapods.
Journal of Experimental Biology: jeb.201525 (advance online publication)
doi: 10.1242/jeb.201525
https://urldefense.proofpoint.com/v2/url?u=https-3A__jeb.biologists.org_content_early_2019_11_26_jeb.201525&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=lEiM1wTBMQLydFGAZ8FBHIUCHxTpkDVecNSA28DGlT8&s=yVXRMsAvKbNSQc4yQ-cgLWOpJxbQKDbTzhpXn2qSOPE&e= 


Comparative analyses of locomotion in tetrapods reveal two patterns of
stride cycle variability. Tachymetabolic tetrapods (birds and mammals) have
lower inter-cycle variation in stride duration than bradymetabolic
tetrapods (amphibians, lizards, turtles, and crocodilians). This pattern
has been linked to the fact that birds and mammals share enlarged
cerebella, relatively enlarged and heavily myelinated Ia afferents, and
γ-motoneurons to their muscle spindles. Tachymetabolic tetrapod lineages
also both possess an encapsulated Golgi tendon morphology, thought to
provide more spatially precise information on muscle tension. The
functional consequence of this derived Golgi tendon morphology has never
been tested. We hypothesized that one advantage of precise information on
muscle tension would be lower and more predictable limb bone stresses,
achieved in tachymetabolic tetrapods by having less variable substrate
reaction forces than bradymetabolic tetrapods. To test this hypothesis, we
analyzed hindlimb substrate reaction forces during locomotion of 55
tetrapod species in a phylogenetic comparative framework. Variation in
species-means of limb loading magnitude and timing confirm that, for most
of the variables analyzed, variance in hindlimb loading and timing is
significantly lower in species with encapsulated versus unencapsulated
Golgi tendon organs. These findings suggest that maintaining predictable
limb loading provides a selective advantage for birds and mammals by
allowing for energy-savings during locomotion, lower limb bone safety
factors, and quicker recovery from perturbations. The importance of
variation in other biomechanical variables in explaining these patterns,
such as posture, effective mechanical advantage, and center-of-mass
mechanics, remains to be clarified.

===

Free pdf:

François Druelle, Jana Goyens, Menelia Vasilopoulou-Kampitsi & Peter Aerts
(2019)
Small vertebrates running on uneven terrain: a biomechanical study of two
differently specialised lacertid lizards.
Scientific Reports 9, Article number: 16858
doi: https://urldefense.proofpoint.com/v2/url?u=https-3A__doi.org_10.1038_s41598-2D019-2D53329-2D5&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=lEiM1wTBMQLydFGAZ8FBHIUCHxTpkDVecNSA28DGlT8&s=ZyEbXdVZzfTOnbTOdWwwn7fFMNVdGuj5eVvct8lnx0k&e= 
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.nature.com_articles_s41598-2D019-2D53329-2D5&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=lEiM1wTBMQLydFGAZ8FBHIUCHxTpkDVecNSA28DGlT8&s=B09NPm-wIP4vRKMs2AQNzOTgdNwCN3mRJhT_z7SIPgo&e= 

Free pdf:
https://urldefense.proofpoint.com/v2/url?u=https-3A__www.nature.com_articles_s41598-2D019-2D53329-2D5.pdf&d=DwIFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=Ry_mO4IFaUmGof_Yl9MyZgecRCKHn5g4z1CYJgFW9SI&m=lEiM1wTBMQLydFGAZ8FBHIUCHxTpkDVecNSA28DGlT8&s=Q2CkRdcYk9JckZH2GvtusBlAd1XjvQ2S_2hKBFl2GmE&e= 


While running, small animals frequently encounter large terrain variations
relative to their body size, therefore, terrain variations impose important
functional demands on small animals. Nonetheless, we have previously
observed in lizards that running specialists can maintain a surprisingly
good running performance on very uneven terrains. The relatively large
terrain variations are offset by their capacity for leg adjustability that
ensures a ‘smooth ride’ of the centre of mass (CoM). The question as to how
the effect of an uneven terrain on running performance and locomotor costs
differs between species exhibiting diverse body build and locomotor
specializations remains. We hypothesise that specialized runners with long
hind limbs can cross uneven terrain more efficiently than specialized
climbers with a dorso-ventrally flattened body and equally short fore and
hind limbs. This study reports 3D kinematics using high-speed videos (325
Hz) to investigate leg adjustability and CoM movements in two lacertid
lizards (Acanthodactylus boskianus, running specialist; Podarcis muralis,
climbing specialist). We investigated these parameters while the animals
were running on a level surface and over a custom-made uneven terrain. We
analysed the CoM dynamics, we evaluated the fluctuations of the positive
and negative mechanical energy, and we estimated the overall cost of
transport. Firstly, the results reveal that the climbers ran at lower
speeds on flat level terrain but had the same cost of transport as the
runners. Secondly, contrary to the running specialists, the speed was lower
and the energy expenditure higher in the climbing specialists while running
on uneven terrain. While leg movements adjust to the substrates’ variations
and enhance the stability of the CoM in the running specialist, this is not
the case in the climbing specialist. Although their legs are kept more
extended, the amplitude of movement does not change, resulting in an
increase of the movement of the CoM and a decrease in locomotor efficiency.
These results are discussed in light of the respective (micro-)habitat of
these species and suggest that energy economy can also be an important
factor for small vertebrates.