Volume 18 Issue 1 Pages 1 - 53 (April
2001)
Citation: Cowell, D., Thomas, G., Liles, G.,
Bradshaw, A., Midgley, L. & Slater, F. (2001) Monitoring the use
of artificial log pile otter holts using hair analysis from bedding IUCN
Otter Spec. Group Bull. 18(1): 6 - 11
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Monitoring the use of artificial log pile otter
holts using hair analysis from bedding
Danielle Cowell1,
Gavin Thomas1,
Geoff Liles2, Adeline Bradshaw1,
Louise Midgley3 and Fred Slater1
1
School of Biosciences, Cardiff University Field Centre, Newbridge-on-Wye,
Powys, LD1 6NB, UK
2 Otters in Wales, Capel Dewi, Carmarthen,
SA32 8AY, UK
3 Llwyn Ffynnon, Harfod, Llanwrda, SA19 8DT,
UK
(received 12 March 2001, accepted 19 May 2001)
Abstract: Nineteen, approximately ten year
old log pile holts (LPH) in mid-Wales, UK, were dismantled prior
to reconstruction and any bedding from couches removed for
analysis. The plant material making up the bedding was identified
and animal guard hairs contained within it were determined to
species. The bedding material simply consisted of
opportunistically available material with little evident
selection. Hairs of cow and sheep were clearly brought in with the
bedding but it is suggested that hairs of otter, badger, fox, dog,
cat, American mink and polecat indicate use of the LPH by the
species concerned. A possible pine marten record is also
considered.
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INTRODUCTION
Artificial log pile holts (LPH) for use by otters, have been in use
in Wales for well over a decade and, in consequence, some of the first
ones to be erected are now in need of refurbishment. It is usually the
forest brash, often used to cover them, which decays first and needs
replacing. After removing the old covering the inner chambers of the LPH
are exposed and Geoff Liles and Louise Midgley of "Otters in
Wales" and their co-workers took the opportunity to remove all
bedding from couches in the chambers of 19 refurbished holts. This
material was taken to Cardiff University's Field Centre at Llysdinam in
mid-Wales where both the botanical make up of the bedding and, in
particular, the identity of any mammal hair incorporated into the
bedding were determined. Although clear from the evidence of spraints
which LPHs had been entered by otters, identification of hair in bedding
would confirm if otters would lie up there and which other species may
have made use of the holts.
MATERIALS AND METHODS
The bedding from each chamber of each holt was collected separately,
and, where the bedding was apparently layered, each layer was separately
bagged. Each sample was loosely sealed into a polythene bag and
appropriately labelled. The samples were then stored in a dry place
until required for analysis. Prior to analysis the samples were stored
for a few days in a deep freeze in order to kill any insects within the
bedding.
Using a powerful desk lamp, each bag of bedding was searched
thoroughly for mammal guard hairs which were usually easier to see when
the light source came from behind. The guard hairs from each bag were
put into a wide necked screw topped jar to await identification and the
bedding material re-bagged for botanical analysis. The finer underhairs
were not collected as they could not be identified. The bedding material
from each sample was separated into its component parts by species and
plant part (e.g. Quercus robur and Salix cinerea, leaves
and twigs). Each component was then weighed.
Analysis of the hairs is a far more exacting process than that of
sorting the plant material in the bedding. Conventional methodologies
generally require that observation of the three layers of the hair, the
cuticle, the cortex and the medulla, each need separate and often
intricate preparation (HAUSMAN, 1930, 1932;
MATHIAK, 1938; WILLIAMSON, 1951; WILDMAN,
1954; FORD and SIMMENS, 1959; SHORT,
1978; TERRINK, 1991).
The key to the hair of West European Mammals by TERRINK
(1991) was useful but techniques in several keys advocated cutting
up to ten cross section slides and ten cuticular slides per hair and
this was unnecessary for most hairs considered and impractical in terms
of time, equipment and the quantity of material for identification. Two
of the present authors devised a specific hair key for this project (COWELL
and THOMAS, 1999) and fast and simple histological techniques for
mounting and identifying hairs, based on a reference collection of hair
compiled by Cardiff University and The National Museum of Wales.
After trials of a range of techniques two were developed which proved
adequate for the purpose providing sufficient information to identify
the range of species we were likely to find in otter holts in Wales.
- Cellulose acetate cast technique (permanent fix - 3 mins to carry
out).
The best techniques for observing the cuticle of hairs are generally
based on making a cast in a suitable medium (e.g. gelatin or nail
varnish) (WILDMAN, 1954; WILLIAMSON,
1951; TERRINK, 1991). Our technique
involved the use of cellulose acetate sheet, which was used for
casts but initially used to observe the medulla. A 5mm wide strip of
cellulose acetate sheet was cut to a length slightly shorter than a
microscope slide. Using a pipette, acetone was thoroughly coated
along the length of the slide and the cellulose acetate strip
immediately
laid in the liquid lowering it on from one end of the slide.
Superfluous acetone was poured or blotted off. The acetate strip was
then attached to the slide. The hair was then laid lengthways on the
acetate strip securing the tip with a drop of acetone. The hair is
then stretched using forceps and the base fixed with acetone, as at
the tip, then the entire length of the hair is flooded with acetone.
Another cellulose acetate strip of approximately the same dimensions
is placed on top of the hair. The hair is then sandwiched between
two fused strips of acetate allowing the medullary structure to be
seen. The technique can be used with several hairs at a time and
takes about three minutes to carry out. To get a cast of the hair do
not use the second acetate strip but after fixing the hair with
acetone wait two minutes, gently peel the hair away avoiding damage
to the distal end, then refix the hair alongside the cast for future
reference.
- The "Sellotape" method - semi-permanent. Time taken - 30
seconds.
A simple and fast technique for making semi-permanent mounts
involved the use of clear adhesive tape (Sellotape). The hairs were
arranged along the length of a glass slide and a length of Sellotape
the same length as the slide was held at each end and very rapidly
put on to the slide to avoid hair movement due to static
electricity. The tape was pressed and rubbed firmly down over the
hairs to avoid air bubbles. For most species cuticular and medullary
structures can be seen. Using TERRINK (1991)
and our own key (COWELL and THOMAS, 1999) the
hair samples were individually identified.
RESULTS
- Bedding materials:
For each chamber of each holt, and, where appropriate, each layer of
each couch of bedding, a species list of plant material present was
constructed and quantified by weight. Detailed results would be
inappropriate and repetitive but several general observations can be
made. Many couches consisted of fine twigs and leaves of the brash
species used to cover the LPH. These were probably collected within
the holt. As the covering brash is usually of local origin some of
the material such as Salix, Alnus and Quercus
leaves could have been brought in from outside the holt.
Other bedding material reflected the location of the holt. Where
wetland with Phragmites or Phalaris was nearby these
two grasses frequently predominated in the bedding. Where the
surroundings were grassland Agrostis, Holcus and the
rush Juncus effusus were frequent. In some cases the mosses
Rhytidiadelphus squarrosus and Thuidium tamariscinum
typical of deciduous woodland floors in mid-Wales were abundant.
Occasionally other debris was found in the bedding including black
polythene silage wrapping, clear polythene sheet, red polystyrene
baler twine and expanded polystyrene cup fragments. In many cases
the lower layers of the couch were well rotted with fresher material
above indicating fairly long continued use of that site.
- Hairs:
The types of hairs found in the 19 holts examined are listed in
Table 1. A number of holts were unused by otters but all contained
some hairs although the dog (Canis) hairs probably came from
the animal owned by one of the authors, which was generally present
when holts were refurbished. Similarly human (Homo) hair is
probably contamination during holt demolition and sample collection
process.
Table 1. Hair types
found in the 19 holts examined |
|
Holt No. |
Hair present of |
|
1 |
Lutra, Vulpes, Bos. Canis |
2 |
Lutra. Bos |
3 |
Lutra, Bos, Canis, Muridae, Homo, feathers |
4 |
Meles, Bos, Canis, Muridae, Ovis, Oryctolagus |
5 |
Lutra, Bos, Felis, Oryctolagus |
6 |
Bos, minimal bedding |
7 |
Lutra, Meles |
8 |
Lutra, Bos, Oryctolagus |
9 |
Lutra, Bos, Meles, feathers |
10 |
Felis, Canis, Mustela putorius, Vulpes |
11 |
Lutra, Bos, Canis, Felis, Homo, Mustela vison |
12 |
Lutra, Bos, Mustela vison, Canis |
13 |
Felis, Bos |
14 |
Lutra, Bos, Canis, Muridae, Ovis |
15 |
Lutra, Bos, Ovis |
16 |
Ovis, Canis, Oryctolagus, Martes martes |
17 |
Canis |
18 |
Lutra |
19 |
Lutra, Bos |
|
DISCUSSION
The provision of LPHs for otters has almost certainly been an aid to
their recovery in England and in Wales (ANDREWS et
al., 1993; STRACHAN and JEFFERIES, 1996)
providing refuge particularly in places where natural holts are scarce.
Although several of the authors are familiar with otter couches in open
cover e.g. Phragmites beds, little is reported of their couches
within holts in general and LPHs in particular. Our results suggest that
the otter might first utilise the plant fragments which originate from
the brash used to cover the LPH and which subsequently fall inside
accounting for the frequent use of coniferous leaves and fine twigs
where these are LPH construction materials. Because the bases of some
couches are well rotted with fresher material above, it would suggest
that these couches are renewed as necessary. Clearly much of the
material comes opportunistically from the immediate environs of the holt
as evidenced by the presence of cattle (Bos) and sheep (Ovis)
fibres. The source of the dog hairs has been suggested as belonging to
the LPH reconstruction crew. Cat (Felis) hair probably represents
the fact that cats are the commonest larger mammal to be seen in the
countryside by both day and night even at distances of over a kilometre
from the nearest house (SLATER, 1994) and might
therefore be expected to explore most areas in the course of time.
Otters clearly used most LPHs and if dog, cattle and sheep hair are
excluded as coming from external sources, several holts were used
exclusively by otters. Although the bedding was generally free of
spraints, the occasional occurrence of broken amphibian bones might
suggest occasional faecal contamination and might account for the small
quantities of "mouse" (Muridae) and rabbit (Oryctolagus)
hair and unidentified "feathers." Having accounted for the
presence a range of possibly non-resident species, the presence of fox (Vulpes),
badger (Meles), mink and polecat (Mustela sp.) suggested
that LPHs offer sanctuary to most of the larger carnivorous mammals
found in Wales. The record of pine marten (Martes martes), one of
the rarest mammals in Wales, is one which needs reconfirmation. It was
recorded from a part of Wales where the species has been recorded in
recent times and, if the record proved to be correct, then the use of
LPHs might be targeted into other non-riparian habitats for the benefit
of other vulnerable species.
REFERENCES
Andrews, E., Howell, P. & Johnson, K.
1993. Otter Survey of Wales. 1991. Vincent Wildlife Trust, London.
Cowell, D. & Thomas, G. 1999. A key to
the guard hairs of British canids and mustelids. Brit. Wildl. 11,
118-120.
Ford, J.E. & Simmens, S.C. 1959. Fibre
section cutting by the plate method. J. Text. Inst. Proc. 50,
148-158.
Hausman, L.A. 1930. Recent studies of
hair structure relationships. Scient. Monthly. 30,
258-277.
Hausman, L.A. 1932. The cortical fusi of
mammalian hair shafts. Am. Nat. 66, 461-158.
Short, H.L. 1978. Analysis of cuticular
scales on hairs using the scanning electron microscope. J. Mamm. 59,
261-267.
Slater, P.M. 1994. Wildlife Road Casualties.
Brit. Wildl. 5, 214-221.
Strachan, R. & Jefferies, D.J. 1996.
Otter Survey of England 1991-1994. Vincent Wildlife Trust, London.
Terrink, B.J. 1991. Atlas and
Identification Key to Hair of West European Mammals. Cambridge
University Press. Cambridge.
Wildman, A.B. 1954. The microscopy of
animal textile fibres. Wool Industry Research Association. Leeds.
Williamson, V.H.H. 1951. Determination
of hairs by impressions. J. Mamm. 32, 80-85.
Résumé :Étudier l'Utilisation des Catiches
Artificielles en Rondins par l'Examen des Poils de Litière
Au Pays de Galles, 19 caliches artificielles en empilements de rondins (LPH),
construites environ 10 ans auparavant, ont été démantelées avant
reconstruction, et à cette occasion la totalité des litières a été
prélevée pour analyse. Le matériel constitutif de ces litières a
été identifié, y compris les poils de mammifères pour diagnose
spécifique. Le matériel de base semble être amassé de façon
opportuniste par l'occupant, sans sélection nette. Des poils de bovins
ou de moutons sont distinctement apportés et nous suggérons que la
présence, dans la litière, de poils de loutre, blaireau, renard, chien,
chat, vison américain ou putois est un indice d'utilisation du gîte
concerné par l'espèce en question. Un cas possible de martre a été
aussi envisagé.
Revenez au dessus
Resumen: Monitoreo del Uso de
Madrigueras Artificiales De Nutrias Utilizando Análisis de Pelos del
Lecho
En Gales UK, 19 madrigueras artificial de madera (LPH) de
aproximadamente 10 años de edad fueron desmanteladas antes de ser
reconstruidas y todo lecho en las madrigueras fue recogido para ser
analizado. Se identificó el material vegetal constituyente de los
lechos y los pelos guardianes de animales contenidos dentro de este fue
determinado hasta el nivel de especie. El material de los lechos
consistió simplemente en el material disponible oportunamente, con poca
evidencia de selección. Los pelos de vacas y ovejas fueron claramente
acarreados con el lecho, pero se sugiere que los pelos de nutrias,
tejones, perros, zorros, gatos visones americanos y turones indican el
uso de los LPH por estas especies. Un posible registro de marta también
es considerado.
Vuelva a la tapa
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