Tree hollow
A tree hollow or tree hole is a semi-enclosed cavity which has naturally formed in the trunk or branch of a tree. They are found mainly in old trees, whether living or not. Hollows form in many species of trees, and are a prominent feature of natural forests and woodlands, and act as a resource or habitat for a number of vertebrate and invertebrate animals.[1]
Hollows may form as the result of physiological stress from natural forces causing the excavating and exposure of the
The size of hollows may depend on the age of the tree. For example, eucalypts develop hollows at all ages, but only from when the trees are 120 years old do they form hollows suitable for vertebrates, and it may take 220 years for hollows suitable for larger species to form.[1]
Hollows in fallen timber are also very important for animals such as
Hollows are an important habitat for many wildlife species, especially where the use of hollows is obligate, as this means no other resource would be a feasible substitute. Animals may use hollows as
Animals will select a hollow based on factors including entrance size and shape, depth, and degree of insulation. Such factors greatly affect the frequency and seasonality of hollow use.[3]
Especially in Europe, entomologists are interested in the use of hollows by invertebrates. One beetle associated with hollow trees, Osmoderma eremita, has been given the highest priority according to the European Union's Habitat Directive.
Description
A tree hollow is a cavity in a living
Artificial hollows
Animals have been found to use artificial structures as substitutes for hollows. For example, pygmy possums in the chute of a grain silo; or pardalotes in the top, horizontal pipe of a children's swing. Purpose-built nest boxes, such as birdhouses and bat tubes,[8] are also constructed for conservation and for wildlife observation. The size of the nest box, entry hole and placement height may be chosen in consideration of certain species. Natural hollows are still generally preferred for habitat conservation.[9]
Actual tree hollows can be created artificially by cutting into trees with chainsaws and partly covering the resulting hollows with timber faceplates.[10][11] These are readily used by arboreal animals including mammals and birds.[10][11] Compared to nest boxes, they last longer and give better protection from external temperatures.[10]
Around the world
Conservation of hollow-using fauna is an issue in many parts of the world. In North America, recovery of the
Australia
In
Threats to hollows include: native forest
Russia, China, Korea
Asian black bears, also known as Himalayan bears (Lat.: Ursus thibetanus), in northern parts of their range, such as Russian province Primorye, China, and both Koreas, prefer spend winter periods in large tree hollows, where females also give birth to cubs. Threats include massive deforestation in these countries, combined with direct poaching of wintering bears—with selective destruction of the best hollow trees. In Russia, attempts (sometimes successful) are made to restore such broken trees.[12] Unfortunately, only a small portion of all damaged trees can be restored in Primorye, where forests are basically logged without taking to account needs of large fauna.[citation needed]
Gallery
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A river red gum, with hollows. The younger trees surrounding it would generally not yet have developed hollows suitable for vertebrate species.
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Hollows excavated by the lesser spotted woodpecker (Picoides minor). Also fungus, which may also help in the formation of hollows through the decomposition of heartwood.
See also
References
- ^ ISBN 0-643-06705-1.
- ^ a b "Tree hollows and wildlife conservation in Australia". NSW National Parks and Wildlife Service. Retrieved 2007-06-19. Includes table of animal groups.
- ^ Stephen Platt. "Wildlife needs natural tree hollows". Department of Primary Industries. Archived from the original on 2007-05-19. Retrieved 2007-06-19. Includes a list of Victorian hollow-using animals.
- ^ Derraik, J.G.B. & A.C.G. Heath. 2005. Immature Diptera (excluding Culicidae) inhabiting phytotelmata in the Auckland and Wellington regions. New Zealand Journal of Freshwater and Marine Research, 39: 981-987.
- ^ Fashing, N.J. 1998. Functional morphology as an aid in determining trophic behaviour: the placement of astigmatic mites in food webs of waterfilled tree-hole communities. Experimental & Applied Acarology, 22: 435–453.
- ISBN 0-521-77316-4.
- ^ "Blood Earth: Hollow trees that host bats benefit from free fertiliser". The Economist. 27 June 2015. Retrieved 30 July 2015.
- ^ Nicholls, Felicity (July–August 2002). "Bat Tubes" (PDF). Land for Wildlife News, NRE. 5 (2): 5. Archived from the original (PDF) on 2007-09-26. Retrieved 2007-06-24., Vol. 5, No. 2, July/August 2002
- ^ a b Hussey, Penny (April 2005). "Tree Hollows & Wildlife". NatureBase Wildlife Notes (15). Retrieved 2007-06-19.
- ^ a b c SCIMEX (15 June 2021). "When natural tree hollows disappear, chainsaw cut-outs are good substitute for tree-climbing mammals". Scimex. Retrieved 2022-07-19.
- ^ .
- ^ Denning trees of Himalayan bears are being restored in Primorye. (in Russian; Cyrillic Windows-1251)