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Mechanical design of hedgehog spines and porcupine quills

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Abstract and Figures

The spines or quills of hedgehogs and porcupines are morphologically and mechanically different. In simple terms, it seems that the quills of porcupines are proportioned to be as long as possible without bending too easily when loaded axially. By contrast, the spines of the hedgehog are as short as possible while still able to bend when loaded axially. In addition, the hedgehog spines have an internal morphology which delays the onset of local buckling under these loads, thus enabling the spines to absorb larger amounts of mechanical energy. By contrast, the quills of Hystrix are designed to break at the tip. Thus, whilst the quills of the porcupine seem to be well adapted for keeping an enemy as far away as possible, the spines of the hedgehog probably have this as an incidental function. Their main function is much more likely to be that of a shock absorber or storage of impact energy when the animal falls from a height, a behavioural attribute which is reportedly common.
Content may be subject to copyright.
J.
Zool.,
Lond. (A)
(1986)
210,55-75
Mechanical design
of
hedgehog spines and porcupine quills
J.
F.
V. VINCENT
AND
P.
OWERS
Biomechanics Group, University
of
Reading, Whiteknights,
PO
Box 228, Reading, RG6 2AJ
(Accepted
16
December
1985)
(With
7
plates and
9
figures in the text)
The spines or quills of hedgehogs and porcupines are morphologically and mechanically dif-
ferent. In simple terms, it seems that the quills of porcupines are proportioned to
be
as long
as
possible without bending too easily when loaded axially. By contrast, the spines of the hedgehog
are as short
as
possible while still able to bend when loaded axially. In addition, the hedgehog
spines have an internal morphology which delays the onset of local buckling under these loads,
thus enabling the spines to absorb larger amounts
of
mechanical energy. By contrast, the quills
of
Hystrix
are designed to break at the tip.
Thus,
whilst the quills
of
the porcupine seem to be
well adapted for keeping an enemy
as
far away as possible, the spines of the hedgehog probably
have this as an incidental function. Their main function is much more likely to be that of a
shock absorber or storage of impact energy when the animal falls from a height, a behavioural
attribute which is reportedly common.
Contents
Page
Introduction
..........................................
55
Materials and methods
....................................
56
Results
..............................................
59
Basic morphology and morphometrics
..........................
59
Mechanical properties
....................................
63
Discussion
............................................
68
Morphology of spines and quills
..............................
68
Mechanical properties of keratin
..............................
70
Euler buckling, struts and columns
............................
71
The function
of
spines and quills
..............................
72
The tips of spines and quills
................................
73
Summary
............................................
73
References
............................................
75
Introduction
In certain mammals, some
of
the hairs are modified into spines or quills. These mammals are
found in three major groups:
Monotremata Tachyglossidae (Echidnas)
Insectivora Tenrecidae (Tenrecs)
Rodentia Erinaceidae (Hedgehogs)
Cricetidae (New World rats and mice)
Muridae (Old World rats and mice)
55
0022-5460/86/009055 +21
SO3.00/0
Q
1986
The Zoological Society
of
London
56
J.
F.
V. VINCENT
AND
P.
OWERS
Rodentia Platacanthomyidae (Spiny dormice)
(cont.)
Hystricidae
(Old
World
porcupines)
Erethizontidae
(New
World
porcupines)
Echimyidae (Spiny rats)
Thryonomyidae (Cane
rats)
In
this study,
we
investigated
some
mechanical properties of the spines, relating these properties
to their morphology
and
their
use
in
defence
and
other
activities.
We
were
therefore interested
only
in
the Monotremata, Insectivora
and,
of
the Rodentia,
the
Hystricidae and Erethizodonti-
dae.
The
spines
from
the
remaining
families
of
the
Rodentia
are
flattened
and
bend
easily and
can
therefore be
of
little
use
in hurting
an
enemy,
though possibly still
of
use as body
armour.
The spines of
the
echidna, hedgehogs
and
tenrecs
are
all
more
or
less uniform: those
of
the
porcupines
can
be
very
varied.
In
the latter
instance,
we
examined only those
spines
which
appeared to
be
of
use
in
defence.
Materials and methods
Spines of the Common echidna
(Tuchyglossus uculeutus),
the Crested porcupine
(Hystrix indicu
x
H.
cristata
hybrid) and the Brazilian Tree porcupine
(Coendou prehensilis)
were obtained from the Zoological
Gardens, Regents Park. Spines of the European hedgehog
(Erinuceus europueus)
were obtained from
fresh road casualties. Spines of the remaining genera used
(Setifer, Echinops, Hemiechinus, Paraechinus,
Atherurus, Trichys, Erethizon
and
Echinoproctu)
were obtained from the British Museum (Natural History).
It was impossible to ascribe these spines to species since they were ones found loose in the drawers
containing the pelts.
Simple measurements were made of the spines using a light microscope and vernier gauge. However, the
internal morphology
of
the spines is complex and this had to be taken into consideration when measuring
the second moment of area
(I),
a shape factor of great importance
in
our analysis. The second moment of
area is the product of the area of any element
of
the section and the square
of
its distance from the neutral
axis (‘middle’) of the column summed for the entire cross-section. Thus the further an element is from the
neutral axis, the greater will its contribution be to the second moment of area. The foam filling of the
porcupine spines was ignored in this calculation but the longitudinal stringers (Fig.
1)
had to be taken into
account. This was done using several different methods. The first-the method of Purslow
&
Vincent
(1978)-involves taking successive strips of the cross-section and multiplying the area of the strip by the
square of the distance of the centroid of the strip from the centre of the spine. Since this method is sensitive
to the width of the strip (i.e. the number of strips the section is divided into), and since for a reasonable
estimate the number of strips must be over
100
or
so,
the estimate of
Z
for the spines with stringers was
performed by a computer program using as the variables the radial length of the stringers and their basal
width, treating the cross-section of the stringer
as
a triangle. Since there is a small fillet at each side of the
base of the stringer, this method will probably give a slight under-estimate. In practise, this method seemed
to overestimate the contribution to
I
made by the stringers, probably because of cumulative accretion of
errors
in
the algorithm used.
A
second method was based
on
the analysis of Harper
&
Flessner (General
cross-section properties by Computer:
pen.
comm.)
which allowed input of the shape of the section from
a digitizer pad. Both methods were checked using scale drawings with simple calculation and direct
measurement (see discussion). An additional parameter, the slenderness ratio, was calculated
as
the ratio
between the least radius
of
gyration of the section of the column
(k)
and the length of the column. The
least radius of gyration can
be
calculated
as
the square root of the ratio between the second moment of
area
(I)
and the cross-sectional area. The slenderness ratio is important when considering the effectiveness
of the spine
or
quill
as
a simple strut
or
column bearing an end load and when choosing the method of
mathematical analysis of the mechanical behaviour (Morley, 1917).
DESIGN
OF
SPINES
AND
QUILLS
Longitudinal
stringer
Septum
FIG.
I.
Diagram summarizing the main morphological features of hedgehog and tenrec spines. It seems likely that
the longitudinal stringers are found
only
in hedgehog spines. The spacing and size of the morphological features varies
from species to species.
Cross-head
*,/,,,,,',,/
FIG.
2.
Test rig used for end loading
of
hedgehog spines (shown solid) and porcupine quill (shown dotted). The
beams supporting the pulleys from the base are not shown for clarity.
For
microscopical analysis, the spines were cut with a razor blade, mounted on a stub with silver paint,
coated with gold and examined in a scanning electron microscope (Jeol T300).
The spines were tested mechanically in a number
of
different ways. The main way was in end loading as
a pin-ended strut. The test rig
(Fig.
2)
was set
up
in an Instron
4202
tension/compression machine. The
specimen was compressed axially by the cross-head moving down at
10
mmlmin. This type
of
loading causes
J.
F.
V. VINCENT AND
P.
OWERS
58
4
I
i
!
!
yJ
i
!
P=O
P<
P,
FIG.
3.
Euler buckling of a simple strut: (a) with the strut initially straight. The strut does not deflect laterally until
the
force
(P)
exceeds the critical buckling
force,
(b)
with the strut initially curved. Any force will cause an increase in
lateral deflection.
This
situation can
be
analysed using Southwell's modification
of
Euler's formula (see text).
the spine to deflect sideways (Fig.
3)
and this movement was detected by a displacement transducer
(RDP
Electronics type
E
300D)
whose
core
was counterbalanced (Fig.
2)
so
that there was no side force on the
spine under test. The base of the test rig was arranged such that, with either
a
hedgehog spine
or
a porcupine
quill, the centre of the spine
or
quill was at the same position. This was achieved by making the base as a
closed-ended cylinder and mounting the end fixing for the hedgehog spine on
a
platform across the mouth
of
the cylinder. In each instance, the ends of the spine
or
quill were located into dimples in the base and
cross-head fixture. The outputs of the Instron load cell and the displacement transducer were combined to
give a force-displacement plot (Fig. 6a). In some experiments, the force at which the spine failed (i.e.
buckled locally) was recorded.
The form of failure being tested is
Euler
buckling.
It is
an
elastic (i.e. recoverable) deformation which
occurs
in a long slender column at
a
critical load,
P,,
whose relationship to the properties of the column is
described by the Euler equation:
n2
EI
P
P,'
-
n
where
E
is Young's modulus
(a
measure of stiffness)
of
the
material
of
the column (in this instance, keratin),
I
is the second moment of area and
I
is the length of the column. The remaining factor,
n,
is a correction
factor for the
type
of end fixing of the column. In our experiments, the ends were unrestrained and the
column was free to rotate axially,
so
n
was unity. The Euler equation is of use in determining
P,,
only if the
column is straight at the start
of
the experiment. Under these circumstances, the column buckles suddenly
as
P,,
is reached and
deflects
laterally. However,
if
the spine is already curved laterally, a modification
of
the Euler formula due
to
Southwell is required (Timoshenko
&
Gere, 1961):
d
=
P,
(dllp)
-e
DESIGN OF SPINES AND QUILLS
59
where
dl
is the lateral deflection at the centre of the column produced by the end load
p
and
e
is the initial
eccentricity. A graph
of
dl
against
(dl/p)
now produces a straight line of slope
Pa
and x-intercept of
e.
This
value of
P,,
can now be inserted into the Euler formula, hence allowing the calculation
of
the flexural
stiffness
(EI)
of the spine. Young’s modulus
E,
is unknown, but
I,
the second moment
of
area, can be
calculated.
For
a simple hollow tube, this is given by:
(R(
114
-
~(2)4)
I=
4
where
R(
1) and R(2) are the outer and inner diameters, respectively,
of
the wall of the spine. The hedgehog
spine tapers at each end but is too short for the tapered ends to be cut
off
and the rest
of
the spine tested in
the Euler mode. A correction can
be
made (Roark
&
Young, 1975) which takes into account the change in
cross-section and the length over which the taper acts. This factor can be inserted into the Euler formula.
Because the ends of the spines and quills tend to fail at small loads, they were removed and replaced
with a hemispherical drop of zinc phosphate dental cement. This ensured that the column was free to
rotate during the test and that the force was fed evenly into the shaft of the quill. The hedgehog spines
were not made any shorter by this operation.
In order to investigate experimentally the function of the internal septa in the hedgehog spine, the ends
of the spines were cut
off
and the septa were removed using a syringe needle. Pins were then glued into the
ends
of
the spines to lengthen them sufficiently to be able to buckle in the Euler mode in the axial
compression test. This was necessary since the intact spine is only just long enough for it to buckle,
so
cutting the ends
off
would shorten it sufficiently to make it into
a
column which would not buckle elastically
(see
Discussion).
Short lengths
of
hedgehog spines were tested in lateral compression in another series
of
experiments, again with and without the septa. In order to reduce variability, these tests were done on
matched pairs
of
spines, two short sections being cut from a spine and one section having the septa
removed.
Strips
of
the outer wall
of
Erinaceus
spine were tested in simple tension, the internal structures being
carefully removed by scraping with
a
razor
blade. The spines of
Erinaceus
were also tested in Cpoint
bending in the Instron. This geometry produces pure bending and no shear in the beam between the loading
points (Fig.
8)
so
that the upper and lower surfaces of the beam are in simple compression and simple
tension, respectively. Great care was taken to make the bearing surfaces of the rig as wide as was necessary
to avoid the collapse of the spine at the bearing points. With the small rig necessary for testing
Erinaceus
spines, the bearing surfaces had to
be
covered with two layers
of
narrow plastic tubing before the spine
could be loaded sufficiently for the spine to fail remotely from the bearing points. The spines were observed
closely during the test and the load noted at which the first compression crease occurred, which was also
marked by an inflection on the force-deflection curve. The stress in the cortex of the spine can be calculated
from simple beam theory. The compressive strength
of
the spine was measured on short columns of length
no more than twice the diameter. In order to ensure that the forces were fed evenly into the wall
of
the
spine, the ends of the spine were glued into blocks of metal using Araldite. Under these circumstances, the
failure always occurred in the part
of
the spine between the blocks, and the ends of the spine were
undefomed.
Results
Basic morphology
and
morphometrics
The spines and quills
of
all the animals investigated are more
or
less cylindrical, tapering at
each end. Some
of
the larger porcupine quills tend towards a more rectangular section in the
middle part. The hedgehog spine has the proximal taper terminated by a bulbous expansion at
its insertion into the pelt (Plate
VII).
The echidna quill is very short and
of
substantial cross-section such that it does not bend and
J.
F.
V. VINCENT
AND
P.
OWERS
PLATE
I.
Transverse (a) and longitudinal
(b)
sections
of
spine
of
a tenrec,
Server
sp. Note the closeness
of
spacing
and relative thinness
of
the septa. Note
also
the way the septa subdivide
on
joining the main wall
of
the spine. Scale line
is
100
prn.
DESIGN
OF
SPINES AND
QUILLS
61
PLATE
11.
Transverse (a) and longitudinal
(b,
c) sections
of
a spine from
Hemiechinus
sp. The septa are more widely
spaced than in the tenrec, are thicker and appear to
be
composed of several fused septa. There are longitudinal elements
(‘stringers’) spaced evenly around the wall of the spine. The insertion of a septum is shown in
more
detail in (c). Scale
tines are all
100
pm.
62
J.
F.
V. VINCENT AND
P.
OWERS
behaves mechanically as a short compressive column. The diameter is of the order
2
mm, the
wall thickness about
0.5
mm. The lumen
of
the quill is filled with foam-like material.
The spines of the tenrecs (Plate
I)
have much thinner walls, with the lumen traversed by septa
which are very closely spaced and not very regular in shape or distribution. The septa subdivide
where they meet the inner wall of the spine and curve round
so
that the fibre directions blend
into each other smoothly. This
also
occurs in spines from the species of hedgehog (Plate
11).
We
did not test the tenrec spines mechanically since they were of unknown age and very dry and
would therefore
be
more brittle than when they are fresh.
TABLE
I
Basic simple measurements
of
spines
of
Erinacem
europaeus
Mean
f
S.D. Number
of
observations
Length of spine
(mm)
20.68
0.558
Diameter of spine
(mm)
1
*
17 0.0364
Wall
thickness
(mm)
0.05
0.00733 21
Cross-section area
(mml)
0.27 0,039
Slenderness ratio
52.07
0.456
The spines of the erinaceids have, in addition to the septa, longitudinal stringers (Plate
11)
which differ in morphology according to species. Two species are shown,
Hemiechinus
sp. and
Erinaceus europaeus.
Several features differ between these two species-the spacing of the septa,
depth of the stringers, and manner of insertion of the septa into the wall of the spine. Only
Erinaceus
provided sufficient spines for us to derive reliable dimensions which are summarized
in Table
I.
The hedgehog spines were sampled from all dorsal areas of the pelt
so
that, in general, the
spines of all hedgehogs are very uniform over the entire back. The length and diameter of
the spine are closely correlated
(Fig.
4),
the regression coefficient being
0.988.
The quills
of
the
I
I
i
I
1
1
*1
1.2
Diameter
(mm)
FIG.
4.
Correlation between length and diameter
of
hedgehog spines taken from
a
single
pelt.
The regression
is
given
byy
=
15.15~+2.93.
DESIGN
OF
SPINES AND
QUILLS
63
various species of porcupine are much more varied in shape and, presumably, function. We
selected ones which were more or less circular (though some were approaching a square section
in the middle of the quill) but
of
much more variable length than the hedgehog spines. The
internal structure is similarly varied, but always includes a foam-like infill (Plate 111). In quills of
Hystrix
there are longitudinal stringers, sometimes with internal stringers not attached directly
to the quill wall (Plate
IV
a, b). Table
I1
summarizes the basic measurements on these quills.
TABLE
I1
Basic simple measurements
of
quills
of
two
species
of
porcupine
Mean
f
S.D.
Number
of
observations
Hystrix indica
x
cristata
Length
of
quill
(mm)
144.0
26.12
Diameter
of
quill (mm) 4.8
1
0.538
Cross-section area (mm2) 3.62 0.833
Slenderness ratio 87.97 7.967
Wall thickness
(mm)
0.2
I3
0.263 7
Coendou prehensilis
Length
of
quill
(mm)
47.19 2.62
Diameter
of
quill (mm) 1.93 0.174
Wall thickness
(mm)
0.08
13
0.0073
8
Cross-section area
(mm2)
0.47 0.065
Slenderness ratio 72.49 644
In
the SEM, the appearance of the wall material after cutting with the razor blade is very
different between the fresh hedgehog and the porcupine species (Plate
V).
Except at the very tip,
the texture of the hedgehog spine keratin looks somewhat soft with blebs of disorganized material
covering the surface (Plate Vb). At the tip of the hedgehog spine and along the length
of
the
porcupine quills, the fracture surface is much more fibrous (Plate Va, c). This suggests that the
matrix material in the bulk of the hedgehog spine is far less well cross-linked and mechanically
more labile than in the porcupine.
A
short experiment in which samples of the wall material
were soaked in water and the water uptake measured showed that, whereas the hedgehog spines
took up about
11%
of their weight in water, the amount taken up by the wall material of
porcupine quills was not detectable.
The correlation between length and diameter of the quills of
Hystrix
is fairly good (Fig.
5)
with
a
correlation coefficient of
0.917.
Coendou
seems to be far more variable in the morphology
of its quills with no correlation between diameter and length, even though the length itself is far
more uniform.
Mechanical properties
The force deflection curves obtained in the Euler buckling tests were replotted according to
the Southwell equation (Fig.
6)
and the critical buckling force estimated from the gradient of
this curve. From this force, Young’s modulus of the keratin of the spine or quill can
be
estimated.
Results are shown in Table
111.
64
J.
F.
V. VINCENT AND P. OWERS
PLATE
111.
Transverse (a)
and
longitudinal
(b,
c) sections of a spine from
Erinaceus europaeus.
The septa are more
widely spaced than in
Seiifer
or
Hemiechinus
and show
a
more
complex insertion into the wall of the spine. At this level,
the fibres can
be
seen to change their orientation through
90"
and run smoothly from the septa into the body wall (c).
The stringers are much deeper than in
Hemiechinus
and are deeply filleted where they join the wall of the spine (arrows).
Scale lines are 100 pm
(a,
b) and
10
pm (c).
TABLE
111
Results from experiments in Euler buckling, showing ihe criii-
cal Euler buckling
force,
the same divided
by
cross-seciion
area, and ihe apparent slirness
of
the wall maierial
of
the
spines and
quills
calculaied from
the
Euler
iests
(see iexi
for
details
of
calculaiion)
Euler buckling Stress at Young's modulus
of
force,
Pm,
buckling wall material (GPa)
Erinaceus
6.54
f
1.99
2.44
11.559
f
0.204
Hystrix
2542
f
5.34 0.712
6.049
f
1.073
Coendou
6.65
f
1.55
1.404
5.564
f
1.143
*S.E.
(MPa) fS.E.
DESlGN
OF
SPINES AND
QUILLS
65
PLATE
IV.
Transverse (a) and longitudinal
(b,
c) sections
of
porcupine quills
(a,
b
Hysrrix
indica
x
crisfata;
c
Coendou prehensilis).
Scale lines are all
100
pm.
66
J.
F.
V. VINCENT AND
P.
OWERS
PLATE
V.
Longitudinal sections of the wall material of the spine
of
Erinaceus europaeus
(a, main shaft;
b,
tip region)
and of the quill of
Hystrix indica
x
crkrata
(c)
showing that in the main shaft of the spine
of
E.
europaeus,
the texture
of
the material is fibrous with a labile matrix, whereas the tip of the same spine and the whole of the porcupine quill is
highly fibrous. Scale lines are all
10
ym.
The reason for the high modulus of the keratin of
Erinaceus
spine wall as calculated from the
Euler tests is explained in the discussion. Simple tensile tests (Table
IV)
show that the real
modulus of the keratin is about a third of this. Notice at present that
Erinaceus
has a high critical
buckling load per unit cross-sectional area compared with the porcupine quills.
In another set of experiments with
Erinaceus
spines, the septa were removed and the critical
buckling load measured. This was no different to the load with the intact spine. However,
if
the
spines were compressed laterally, the force at which the circular cross-section of the spine
TABLE
IV
Simple tensile stiflmss
(Young’s
modulus)
of
the
wall
material
of
bhhaceus
spine
Young’s modulus
kS.D.
Number of tests
@Pa)
Dry
spines
3.155
0.807
4
Wet wines
2.294 0.141
3
DESIGN
OF
SPINES AND
QUILLS
67
200
1
100
I
1
4
5
6
Diameter
(mm)
FIG.
5.
Correlation between length and diameter of quills from an uncertain number of individual Crested porcupine.
The regression is given by
y
=
7.04x+
33.6.
collapsed was reduced by
50%
with the septa removed (Fig.
7,
Table
V).
In addition, the
compressed specimens were different in shape (Fig.
7).
Some spines which had failed by local
buckling were cut to show the septa at the failure site and examined by
SEM
(Plate
VI).
This
confirmed that the spine becomes oval at failure and also showed damage to the septa. Plate
VII
shows the tips of Porcupine quills and the base
of
the spine of
Erinaceus.
The load to compressive failure (i.e. local buckling) in whole spines of
Erinaceus
(Fig.
8)
in four-point bending was measured as
0.392
GPa with standard deviation
0.0276
GPa. The
compressive strength measured directly in short sections of spine was
0.348
GPa with standard
deviation
0.05
17
GPa.
TABLE
V
Effect
of
removal
of
the internal septa
on
the integrity
of
structure
of
the hedgehog spine
Intact Septa
spines destroyed
Compression
to
induce collapse (mm)
0.1
77
f
0.0206 0.176
k
0.0305
Force
(N)
34.07
k3.115
18.36 k2.358
Simple observation of the failure mode of quills of
Hystrix
shows more complex behaviour-
there is a gradient in failure mode
from
base to tip. At its basal half, the quill buckles locally like
a
hedgehog spine and remains longitudinally intact. The top quarter of the quill is much more
likely
to
fracture completely in a brittle fashion. This behaviour has not been quantified further
68
J.
F.
V. VINCENT
AND
P.
OWERS
2ol
0
1
234
Lateral
deflection
(mml
5-
4-
E
E
-
.-
E
3-
5
8
2-
G=
-
E
5
1-
0
I
I
I
I
0.2
0.3
0.4
0.5
J'
##:
,'
0
d//P
(mm
N-')
I
4
FIG.
6.
Graphical analysis of results obtained from the apparatus of Fig.
2:
(a) force-deflection curves;
(b)
the same
curves
replotted according
to
Southwell's analysis. The
slope
of the line is the critical
or
Euler buckling load, which can
now
be
inserted into the
Euler
equation
(see
text).
owing to the complex shape of the quill, but a random sample
of
58
Hystrix
quills had
36%
with
broken tips, suggesting that it is fairly common for the end of the quill to break
off.
We have
never seen a hedgehog spine with
a
broken tip.
Discussion
Morphology
of
spines
and
quills
Spines and quills are all modified hairs made, presumably,
of
alpha keratin. Certainly, the
walls have a fibrous structure. The internal structure
of
both hedgehog and porcupine spines has
408
30
z
2
a,
::
20'
10
0
DESIGN OF SPINES AND
QUILLS
69
I
I
I
Compression
(rnrn)
I
I
0.5
FIG.
7.
Force-deflection curves for hedgehog spines compressed laterally, showing the shapes
of
the compressed
spines with and without the transverse septa.
PLATE
VI.
Transverse section of a spine
of
Erinaceus
showing the deformation at the site of local buckling. Note the
oval shape of the section in (a) and the way the septum has folded along the major axis
of
the oval.
In
the detail (b),
note the transverse tear (arrow) indicating that the septum was stressed in tension. Scale lines are
100
pm.
70
J.
F.
V.
VINCENT AND
P.
OWERS
F
F
FIG.
8.
Geometry
of
four-point bending test
(a)
showing distribution
of
shear (b) anL -Ending moment (c) along
I
ie
beam. The bending moment,
M,
is given by the product
of
the
force
(F)
and the distance from the support
(4.
The
stress in the cortex
of
the beam is given by the expression
My/&
where
I
is the second moment of area and
2y
is the
depth
of
the beam.
been described previously in various degrees of detail (Harrison Matthews, 1952; Mohr, 1964;
Katusic, 1973; Sterba, 1976) but no correlation has been made with the mechanical properties.
Mechanical properties
of
keratin
The mechanical properties reported in this paper are nearly all those of
a
structure (the quill
or spine) or those derived from this structure with, in all probability, incomplete corrections for
the effect of the morphology of the structure. This distinction between material and structure is
an important one. Fraser
&
MacRae (1980) reported tensile and compressive moduli of porcupine
quills at various humidities. Assuming that the longitudinal compressive and tensile moduli are
at small strains and comparable, he gives
a
value for ‘porcupine quill’ (no species mentioned) of
5.8
GPa which agrees well with the figures in Table
111.
Thus, it can
be
safely concluded that the
simple second moment of area of the quill wall accounts for
all
the structural components and
that the foam infill of these quills does not contribute to resistance to elastic buckling. It is still
highly likely, however, that this foam makes a significant contribution in delaying the onset of
local buckling by providing local support to the quill wall. The spines of the hedgehog, however,
give
a
much more complex response, the reason for which is discussed below. Basically, the
modulus of the wall material calculated from the Euler test
is
much greater than that measured
directly in simple tension.
DESIGN
OF
SPINES AND
QUILLS
71
Euler buckling, struts and
columns
In order to appreciate some aspects of
our
results it is necessary to understand the mechanics
of end-loading on struts and columns. The mode of deformation and, therefore, the load at
which deformation will occur, of a pillar, column or strut depends upon a number of factors
(Morley, 1917). Assuming initially that the ends of the column are free to take up any angular
position relative to the load, though not free to move relative to the point at which the load is
applied, the column will be compressed. If the column has a certain minimum slenderness it will
tend to bend sideways and buckle elastically. Above a slenderness ratio of about
80,
Euler’s
formula for the maximum supportable load can be used with some confidence. At a slenderness
ratio of about
40,
under ‘ideal’ conditions,
Euler’s formula ceases
to
be
applicable and the column
will react as a pillar and not bend to one side when subjected to an axial force: instead it will
collapse locally when the compressive
or
shear strength (whichever is the lower) is reached.
However, in the real world, columns with a slenderness ratio between
40
and
80
will not
necessarily conform to Euler’s analysis and, in particular, may well show some of the
characteristics of a column at the lower end of the scale of slenderness ratio. In addition, the
nature of the material from which the column is made will affect the value of slenderness ratio at
which Euler’s analysis ceases to apply. Therefore, the slenderness ratio is a parameter of some
importance in this discussion, more especially as the spines and quills investigated all come into
one part or another of the critical zone of slenderness ratios.
The measurements shown in Tables
I
and
I1
show that the quills of the porcupine have
a
far
higher slenderness ratio than those of the hedgehog, probably just about large enough for the
Euler analysis to be valid. The estimates for the stiffness of keratin of porcupine quills are
reasonable (Fraser
&
MacRae, 1980). However, the slenderness ratio of the hedgehog spine is
relatively small and it is doubtful whether it would buckle elastically if it were straight. The fact
that the spines always have both tip and base slightly to one side means that the force will always
reach the main shaft with slight eccentricity and ensure that it buckles elastically. At the same
time, its low slenderness ratio means that it will support a load more characteristic of a short
column which will necessarily be higher than that of an Euler strut. This accounts for the
apparently anomalous high critical buckling load of the hedgehog spines and also the high
modulus for the keratin, which is obviously an over-estimate, taking the data at face value. In
summary, it appears that, whilst the porcupine quills appear to be designed to be as long as
possible without buckling too easily, the hedgehog spine seems to be made as short as possible
without completely preventing it from buckling, thus enabling it to take a much higher load.
However, there seems to be more to the design
of
the hedgehog spine.
It is evident that the stringers in the spines of the various species of hedgehog, since they
project towards the middle of the spine, contribute little to the second moment of area. A model
calculation shows that, in
Erinaceus,
they may typically be expected to contribute about
25%
of
the cross-sectional area but only
13%
of the second moment of area. If the second moment of
area were
so
important, it would be cheaper
to
increase it by adding material
to
the external
circumference of the spine. It would then
be
possible to increase
I
by the same amount by adding
only
4%
to the area of the cross-section, a sixth
of
that required to form the stringers. Therefore,
the material used to make the stringers is not best placed to increase the second moment of area,
so
that the stringers (and, by implication and experiment, the septa) are not contributing to the
stiffness of the spines in elastic buckling in any simple manner. Close examination of the stringers
and septa reveals that the inner edge of the stringers is reinforced by the branching of the septa,
12
J.
F.
V.
VINCENT AND
P.
OWERS
FIG.
9.
Local buckling
of
a thin-walled cylinder showing the change in cross-section at the site of failure. The change
in shape can
be
resisted by taking the transverse tensile force (arrows) by
a
septum.
giving an inner vertical skin to the spine. The whole spine then starts to resemble a tube rolled
out of corrugated cardboard with the inner surface providing stability against buckling. The
septa, rather more obviously, can retard the onset of local buckling by retaining the circular
cross-section and thus keep the second moment of area higher. They do this by resisting tension
rather than compression, since the septa are thin enough to buckle in compression. Plate
VI
shows this: the septum is folded in the long axis of the oval section and has been torn transversely
to this, showing that it has exceeded its tensile strength. Once the section goes oval, the effective
I
in the direction of the minor axis of the oval is reduced and the spine fails (Fig.
9)
by local
buckling or compression failure. The problem now is, that by resisting local buckling, the spine
has increased the load in the wall of the spine and the mode of failure is going to be more
dependent on the degree of structural stability of the wall and on the compressive strength
of
the
material (a parameter which does not affect resistance to elastic buckling) rather than the stiffness
(which appears in the Euler formula). Experiment shows that the stress at which the spine wall
fails in compression is not significantly different from the true compressive strength, suggesting
that the structure of the wall of the spine is, indeed, very effectively stabilized
so
that the ultimate
properties of the material can
be
expressed. In addition, the stress at buckling of the spine is
only
0.5%
of the compressive strength,
so
that when the spine has exceeded its critical buckling
load
it
can take
200
times that load before failing.
If
the spine were designed to resist loads, then
the critical buckling load would
be
expected to be quite close to the ultimate compressive load.
The function of spines and quills
It thus appears that the spine of
Erinaceus
is designed to absorb energy by buckling elastically,
but only under a relatively high force, and then to deform elastically as far as possible without
failing by local buckling or compressive failure. This mechanical design suggests that the hedge-
hog spine is an elastic strain energy store to protect the animal from impact, either from a
predator or from falling. The uniformity of length of the spines over the dorsal
pelt
supports
this interpretation since the energy storage will be the same no matter how the animal falls.
DESIGN OF SPINES AND QUILLS
13
There are many reports in the literature of hedgehogs climbing up trees or
ivy
and descending
by rolling themselves up and simply dropping to the ground (Harrison Matthews, 1952, 1969),
and Dr P. Morris has told us that he considers the hedgehog to live in a three-dimensional
habitat in that it appears to be totally unafraid of scaling considerable heights
(10
m or more) in
search of food. The only way that the spines can absorb energy is if they are deformed perma-
nently, and it seems to
be
the job of the internal septa to ensure that such deformation occurs
only under extreme conditions. However, if the spines are to absorb energy by reversible (elastic)
strain energy storage, the hedgehog would be expected to bounce. This may occur although we
have not seen it reported. Perhaps it has been dismissed as being unlikely! Another implication
concerns the uniformity of length of the hedgehog spines. It seems logical that other animals
which have a uniform length of spine should be using the spines as shock absorbers and could
therefore be arboreal. Thus
Coendou
is arboreal and
so
are some tenrecs. The extreme stiffness
and bending strength of the offensive spines of
Hystrix
and similar species would
be
expected to
be positively disadvantageous were these animals arboreal: they could well impale themselves on
their own quills since there is nothing like the mushroom-shaped end of the hedgehog spine
(Plate VII) to spread the load into the skin. Additionally, the quills of
Coendou
have a very thin
insertion-perhaps these quills break
off
rather than impale their bearer.
Amongst the hedgehogs examined, transverse septa occur in spines of all the species, but
stringers occur only in the more advanced species. The inference is that the stringers are a more
advanced element. Certainly, as mentioned above and shown in experiment, the septa will delay
the onset of local deformation and
so
would
be
an advantageous design feature for a shock
absorber. Such septa exist in hairs of other Insectivora which are not stiff or protective (Vogel
&
Kopchen,
1978).
The tips
of
spines and
quills
If, as suggested above, the spines and quills of porcupines and hedgehogs have different
functions, it might be expected that this would
be
reflected in other aspects of their morphology.
The nature of the insertion of the spine, alluded to above, seems to
be
one of these aspects.
Another is the nature of the tip of the spine. In both porcupines examined, the tip of the shorter
spines has scales orientated in such a way that the resistance to pushing the tip into the skin of
an aggressor is much less than that of pulling it out (Plate VIIb, c). By contrast, the tips of the
long dorsal quills
of
Hystrix,
which could not possibly resist anything approaching the end-loads
which the shorter quills can accommodate, have no scales and have the orientation of the slight
surface texture reversed (Plate VIIa). Thus it would be more difficult to push them into the skin
than pull them out. The inference is that the shorter porcupine quills are meant to stay stuck in.
The few simple experiments on the fracture mode of the quills of
Hystrix
show also that once
the quill has lodged itself in the skin, the tip is designed to break off and remain in the assailant.
This happens more or less routinely (Po-Chedley
&
Shadle, 1955; Kuntz, 1976). By contrast, the
tips of all hedgehog spines are smooth with no differential friction mechanism.
Summary
We have studied the morphology and mechanical design
of
spines and quills from a number
of species of hedgehog and porcupine, also the echidna. The spines of the latter are massive and
blunt and probably constitute a body armour, as probably do the flattened spines of many
14
J.
F.
V. VINCENT AND
P.
OWERS
PLATE
VII. Tips
of
porcupine quills and the base of a hedgehog
(Erinacew)
spine. The
long
dorsal quills
of
Hystrix
have a fibrous surface texture (a), whereas the shorter quills of
Hystrix,
which are those which can penetrate
skin,
have
a scaley texture
on
the tip (b). In both (a) and (b) the tip of the quill is to the left. The quills of
Coendou
have much
coarser scales (c). The base of a spine of
Erinaceus
(d) shows the broadening which both anchors the spine and prevents
it being pushed into the animal’s body when the spine is loaded
on
its end. All scale lines are
100
pm.
smaller rodents. However, the analysis of the functional design
of
spines and quills leads us to
propose that, in all species of hedgehog examined, and at least one species of porcupine
(Caen-
dou),
they are concerned not
so
much with agonistic behaviour as with absorbing impact in a
fall.
Detailed analysis
of
the spines of
Erinaceus
from both morphological and mechanical aspects
shows that they deflect elastically as end-loaded struts, supporting the maximum load which is
possible in this mode of deformation. They do this by working to the limits of shape (they are
only just long enough to deflect in the Euler mode and always take the load
off
centre) and
DESIGN OF SPINES AND QUILLS
75
material (the walls of the spine are
so
well supported that they do not fail until the ultimate
compressive strength of the material is reached).
Our
work confirms the general opinion that the shorter quills of porcupines such as
Hystrix
are adapted as weapons. In addition, we note that these quills are as long as might be expected
from the theory of design of end-loaded struts without tending to deflect laterally to excess.
Thus, there is sufficient resistance to end-loading to allow the tip of the quill to penetrate the
skin
of
an assailant whilst maintaining the quill at maximum design length. This much is common
observation. In addition, the failure mode
of
the quill varies along its length such that the distal
quarter can break in bending on the tension surface and leave the tip of the spine in the skin of
the assailant. The more proximal parts
of
the quill fail more readily in compression and do not
fracture. The material basis of this differentiation remains to be established.
We
thank
Dr Brian Bertram
of
the Zoological Society
of
London
for
supply
of
porcupine quills, Dr
Paula Jenkins
of
the British Museum (Natural History) for supply
of
quills
and spines for microscopical
analysis
and Dr Giorgio Jeronimidis for much help
in
discussion
and analysis. The Instron
4202
test
rig
was
largely
funded
by
the
Royal
Society.
Dr H. Flessner
can
be
contacted at the University
of
Hamburg, Fachbereich Informatik, Troplowitz-
strasse
7,
2000
Hamburg
54,
West Germany.
REFERENCES
Fraser, R. D. B.
&
MacRae,
T.
P.
(1980).
Keratins.
Symp. Soc. exp.
Eiol.
34:
21 1-246.
Harrison Matthews, L.
(1952).
British
mammals.
London: Collins.
Harrison Matthews, L.
(1969).
The
life
of
mammals
1.
London: Weidenfeld
&
Nicolson.
Katusic,
J.
(1973).
Leichtbaukonstruktionen bei Saugetierstacheln.
Microkosmos
63
300-303.
Kuntz, B.
(1976).
Quills among the needles.
Wyoming Wildl.
40:
12-15.
Mohr,
E.
(1964).
Die Korperbedeckung der Stachelschweine.
Z. Saugetierk.
29
17-33.
Morley, A.
(1917).
Strength
of
materials.
London: Longmans, Green
&
Co.
Po-Chedley, D.
S.
&
Shadle, A. R.
(1955).
Pelage of the porcupine,
Erethizon dorsatum dorsarwn.
J.
Mamm.
56:
84-95.
Purslow, P. P.
&
Vincent,
J.
F.
V.
(1978).
Mechanical properties of primary feathers from the pigeon.
J.
exp.
Eiol.
72
Roark, R.
J.
&
Young, W.
C.
(1975).
Formulas
for
stress andstrain.
5th edn. Tokyo: McGraw-Hill Kogakusha Ltd.
Sterba,
0.
(1976).
Zur
Entstehung der Stacheln
bei
der Gattung
Erinaceus
(Mammalia, Insectivora).
Zool. Listy
25
33-
Timoshenko,
S.
P.
&
Gere,
J.
M.
(1961).
Theory
of
elastic stability.
2nd
edn. New York: McGraw-Hill Book Co. Ltd.
Vogel, P.
&
Kopchen, B.
(1978).
Besondere Haarstrukturen der Soricidae (Mammalia, Insectivora) und ihre taxo-
251 -260.
38.
nomische Deutung.
Zoomorphologie
89:
47-56.
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Thesis
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The envelope is a concept that defines an interface between an internal and external environment. They can be ‘living’ (skin, hair, feather, bark, membrane of a cell) or ‘non-living’ (egg, animal architecture, shell) or man-made design (packaging, building facade, car body, etc). Nowadays, industry, architecture and product design are particularly interested in replicating the properties of biological envelopes in order to improve the performance of man-made envelopes (mechanical resistance, acoustic and thermal insulation, water and air permeability, etc.). However, these bio-inspired researches are often inspired by the same panel of biological organisms characterized according to a single-criterion approach. This research first presents a comparative analysis of bio-inspired building skins built over the last fifty years in chapter 1. The second chapter provides a multi-criteria analysis of a selection of ten types of biological envelopes of eukaryotes in terrestrial environment and on a macroscopic scale (skin, hair, feathers, bark, etc.). By classifying these organisms using several criteria of analysis (functions of regulation, time scale, size scale), this research enhances connexions between life and design sciences. The third chapter proposes a multi-criteria analysis tool for biological organisms allowing a systemic understanding of living beings in a perspective of biological properties transfer for a multi-criteria design. Last section of this research discusses the ethical aspects of biomimetics and the relevance of the acquisition of new biological data, the taxonomic bias and the methodological aspects of the approach in architecture. Online access: https://hal.archives-ouvertes.fr/tel-03558596
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Nature provides an infinite source of inspiration for innovative designs that may be required to tackle the social, economic, and environmental challenges the world faces. Despite the surging popularity and prevalence, the discipline of bioinspiration is limited in unleashing its full potential by the inadequate understanding of biological and evolutionary concepts, often leading to suboptimal solutions and a lack of further development toward successful products. Here, the constraints and limitations that pose potential pitfalls for bioinspiration, but are generally overlooked by most practitioners of bioin-spiration, are discussed. It is highlighted that an awareness of biodiversity is key to address this issue, and ultimately to the successful application of bioinspiration in general. Furthermore, a practical approach to the analysis of biodiversity information is provided and attention is drawn to opportunities for improving the translation of biological knowledge into innovative solutions. Primary emphasis is placed on direct bioinspired product innovations, though many of the concepts central to the ideas are applicable to the wider domain of bioinspired materials science, chemical, and systems engineering, among others. With this perspective, the guiding thread that will enable to escape the labyrinth of bioinspiration and follow the right track to successful innovation is brought back.
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SUMMARY The morphology of the primary feather shaft from the pigeon wing has been examined and its salient features noted. The cortex (outer wall) of the shaft appeared to be the most significant feature in relation to bending behaviour and was analysed quantitatively. A model that simulated bending of the shaft was made using this analysis and upon comparison of simulated results with observed bending behaviour it is shown that the shape and size of the cortex does indeed account for the majority of bending behaviour. The model does not include torsional effects and the effects of the pithy medulla and the transverse septa, but the magnitude of these effects is considered to be small in comparison with that of the cortex considered in simple bending. Differences in the shape of the cortex in the outermost primary and those proximal to it are shown to account for different mechanical properties and possible reasons for this are given. The shape and size of the cortex, as meas- ured by its second moment of area, is shown to have some relation to the body weight of the bird.
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The following study should clear up the structures of the H-shaped profile found in the hairs of some shrews and show if it has a taxonomic signification. Therefore we studied the concerned hair structures by scanning electron microscopy in 8 genera. The special hair-shape, which is confined to the terminal segment of guard hairs, is found in the species of the following genera:Sorex, Neomys, Blarina andCryptotis, all members of the subfamily Soricinae. All the examined members of the subfamily Crocidurinae, i.e.Crocidura, Praesorex, Suncus andSylvisorex show a simple hair shape. The H-shaped hair characterizes the Soricinae as a monophyletic unity. Yet, the morphological criteria of hair complete the osteological criteria of Repenning (1967) an plead for the validitiy of the often refuted subfamilies.
Die Körperbedeckung der Stächelschweine
  • Mohr E.
Mohr, E. (1964). Die Korperbedeckung der Stachelschweine. Z. Saugetierk. 2 9 17-33.
  • J Katusic
Katusic, J. (1973). Leichtbaukonstruktionen bei Saugetierstacheln. Microkosmos 6 3 300-303.