bio-floors in animal enclosures 14 may 2020€¦ · 14/05/2020 · introduction 1.1 definition...

Bio-floorsin Animal Enclosures

14 May 2020

Monika Fiby

Recommendations for Using Bio-floor

Credit note

The growing expertise on the use and the many advantages of bio-floors, are the reasons tocompile the following recommendations. Much of it is based on information gained from personalinterviews and found in the EZG - EAZA Zoohorticulture Group from people who have practicalexperience.

I am obliged to following persons for sharing their expertise:

Stephen Butler, Dip Hort Kew, retired Curator of Horticulture, Dublin ZooCarsten Knott, Animal Science, Welfare & Projects Manager, Christchurch ZooJörg Kubacki, Inspector, Heidelberg ZooSandra Reichler, Scientific Assistant and Curator, Heidelberg ZooRudolf Wicker, retired Vice Director and Curator, Frankfurt Zoo

Jonas Homburg generously shared photos for this paper.

Cover illustration: Bark mulch, wikimedia by Apostoloff, 2009Illustration below: © Monika Fiby

Dipl.Ing. Monika Fiby, MLALandscape Architect, Zoo Design, Consulting

Contact: [email protected]

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Inhalt

1. Introduction ............................................................................................................................ 41.1 Definition .......................................................................................................................... 41.2 History ............................................................................................................................. 41.3 Advantages ...................................................................................................................... 41.4 Disadvantages ................................................................................................................. 4

2. Types of Bio-floor ................................................................................................................... 52.1 Sand ................................................................................................................................ 52.2 Soil ................................................................................................................................... 52.3 Mulch ............................................................................................................................... 5

3. Mulch quality .......................................................................................................................... 53.1 Production ....................................................................................................................... 53.2 Biological activity ............................................................................................................. 5

4. Deep mulch planning .............................................................................................................. 64.1 Criteria for choosing mulch in animal enclosures ............................................................. 64.2 Installation ....................................................................................................................... 64.3 Renovation ...................................................................................................................... 74.4 Maintenance .................................................................................................................... 9

5. Case studies ........................................................................................................................ 105.1 Primates ........................................................................................................................ 105.2 Big Cats ......................................................................................................................... 145.3 Herbivores ..................................................................................................................... 145.4 Birds, reptiles, amphibia ................................................................................................ 18

6. Development ........................................................................................................................ 19

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1. Introduction

1.1 Definition

Bio-floor is a thick layer of substrate (mulch, sand, soil etc.) with biological activity that is used inindoor enclosures to break down animal urine and faeces. The substrate may be left for a fewweeks or for years, depending on space, animal species, bio-floor material and the implementedsystem.

The Dictionary of Zoo Biology and Animal Management by Paul A. Rees (Wiley-Blackwell, 2013)defines bio-floor as „self-cleaning floor used in animal enclosures which functions as a biologicalsystem to prevent build-up of pathogens or parasite infestation. It consists of a top layer of peat,wood chips or similar material laying on top of a filterpad on a concrete floor with a drain below thepad.“ A reference to indoor animal enclosures is missing in this definition, but assumably implicit.

The expression deep litter has been used in zoos mostly for mulch bedding. Since litter issynonymous for garbage, waste, refuse or rubbish, the expressions bio-floor or deep mulch arepreferable for substrates with biological activity that are used in animal enclosures.

1.2 History

Deep straw bedding with biological activity has been used in stables for domestic stock longbefore zoos got interested in this type of bedding. In barns that are designed for deep strawbedding, a thick layer of straw is moving downwards on a tilted floor by the hooves of cattle orhorses. The straw is replenished at the high end and removed at the low end of the barn. Thespeed of exchange of the bedding depends on the thickness of the layer and the angle of the floor.The biological activity of bacteria, fungi, worms and insects in the straw decomposes manuresufficiently to maintain required hygienic standards.

1.3 Advantages

Deep mulch harbours organisms that recycle excrement and urine and absorbs bad smells. Theuse of deep mulch saves water for hosing enclosures and staff time. Moreover, deep mulchsoftens the space visually and accustically. It provides structure, is foot friendly and soft andproduces humidity and a little warmth. It also offers enrichment opportunities when food isdispersed or buried.

1.4 Disadvantages

Deep mulch needs regular maintenance, however much less time and effort than regular hosing. Itcan harbour fungi and pest animals such as rodents, cockroaches, parasites such as roundworm(Ascaris lumbricoides), and tropical ants (Pheidole bilimeki, Technomyrmex vitiensis). Generallyharmless woodlice (sub order Oniscidea) can build up to very large numbers, and can be an issueif contaminating animal food. Slugs can become a food contamination problem when conditionsare moist enough for them.

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2. Types of Bio-floor

2.1 Sand

Sand does not bed down and can be used with one and more metres of depth. Sand for golfcourses has graded large size particles with excellent drainage properties. Drains along the basetake excess water away. Mist units can be used to keep the sand surface moist when it gets toodusty.

Sand has been used for elephants at Copenhagen Zoo and Dublin Zoo. Sandy loam is the flooringfor rhinoceros at Magdeburg Zoo.

2.2 Soil

Soil can be used as the basis for bio-floor with or without a concrete base. In both cases a gooddrainage system is essential. Bio-floor can also be a soil-mix with mulch on top for plants.

Soil has been used for cats and primates at Frankfurt Zoo and for chimpanzees at OsnabrueckZoo.

2.3 Mulch

Deep mulch contains wood chips and bark in various qualities and compositions, depending on itsdepth and the species it is used for.

Zoos that have been using deep mulch in Europe for a long time are Copenhagen, Dublin,Frankfurt, Heidelberg, Magdeburg and Zagreb to name just a few.

3. Mulch quality

3.1 Production

There are different methods of removing bark from timber.

High pressure water can result in a very wet substrate that may remain wet, and can have a heavyodour.

Mechanically removed bark is a much better material for deep mulch. However, fine particles in itspeed up decomposition and should be screened out.

A cheaper option, but with highly variable quality, can be shredded material from tree surgeons. Itsnature – coarse or fine material – will depend on the sharpness of the chipping blades, the treematerial itself can be conifer or broadleaf, and the share of leaves in it depends on the time ofyear of production. During summer, any bulk of leaves will cause the chippings to heat upconsiderably. They can be heaped outside and used when cool, but this material tends to rot veryquickly to an almost peat-like substrate. Care must be taken too to not take in potentially toxicplant material such as yew Taxus baccata or elderberry Sambucus nigra. Thorny trees likehawthorn Crataegus monogyna can cause problems with animal feet.

3.2 Biological activity

Bark mulch used for garden mulching to reduce weeds and watering varies in particle size. A mixof particle sizes beds down better to exclude light and reduce weeds. Larger grade bark with nofines is used as a surface for playgrounds. It is poriferous and much looser until it breaks down.

Tree chippings will normally hold water much longer, as they have more small particles of leaf and

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bark, but will probably need to be removed more often when wet.

Wood chips with no leaves, few small twigs and no bark rot much slower due to few fine particles,little share of soft material, and more air spaces to dry.

Mulch that rots slowly needs replacing less often, which means less work, less waste disposal,and less cost on both.

It is advisable to use bark mulch with a high share in tannic acid such as oak and evergreen trees.Pine (Pinus sp.) bark is longlasting and has a structure with many openings, layers and slits thatcontain well aerated areas as well as anaerobic areas, so that nitrifiers and denitrifiers are able tosettle and function. While Pine bark is coarse it can be mixed with a finer material such as Larch(Larix sp.) bark.

It is important not to use sterile mulch because the biocides used for its treatment also harm usefulbacteria and can damage the digestive system of herbivores. Sterile mulch is also more receptiveto mildew. Common mulch for landscaping with one to four centimetre pieces is fine. Thecoarseness of the material should be adjusted to the species using it.

4. Deep mulch planning

4.1 Criteria for choosing mulch in animal enclosures

• Animal species in the enclosure do not take in mulch when feeding from the floor

• Availability of bark mulch from untreated trees with tannin (evergreen species)

• Accessibility to the enclosure for taking in and out the mulch

• Functioning drainage of the enclosure

• Effective pest control

4.2 Installation

Fifty centimetres seem to be the minimum depth to keep the mulch in place for eight to ten yearswithout complete replacement.

Vehicle access is useful, saving time, energy, and reducing manual handling, for bringing in andtaking out mulch.

Good drainage is essential. Drainage mats like those used for green roofs are cost efficient. ZooFrankfurt uses drainage panels of three centimetres thickness – perforated synthetic tiles that arewater resistent. Geotextile needs to keep mulch off the drainage layer that diverts the water to thedrainage outlet. Using such mats may however limit the use of machinery for cleaning orreplenishing the mulch. A paddock flooring system of rubber hole mats on top of the drainage isuseful.

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Wood chips degrade much slower than bark chips and therefore should not be used to start deepmulch. One year after installation and later on, wood chips with high tannic acidity (oak,evergreens) can be added. Wood chips don‘t compact as much and keep the structure andaeration of the mulch better than bark chips. Attention needs to be given to the origin of woodchips to make sure that there is no problem with resin or toxicity of tree species.

4.3 Renovation

When installing bio-floor into existing enclosures, areas in front of shift doors and doors are keptopen by separating them with boards, trunks or stones from mulch.

At Osnabrueck Zoo the concrete floor of monkey exhibits was one metre below visitor floor level.During renovation, geotextile was installed to keep the drains open. A fifty centimetre layer ofbranches of spruce and fir was installed for aeration and drainage. A layer of fifty centimetres barkchips on top of the branches is refilled as needed.

Concrete flooring was cut out in 2017 and replaced by sand at the elephant house that was built atOsnabrueck Zoo in 1998.

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Photo 1: 3cm drainage mat © Monika Fiby, 2006


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Photo 2: Renovated tiger quarters at Heidelberg Zoo © Jonas Homburg, 2017

Photo 3: Gorilla exhibit at Heidelberg Zoo© Jonas Homburg, 2017


4.4 Maintenance

Some mulch is taken away with the cleaning and needs to be replaced as well as mulch in wet orsoiled areas. Budget needs to be reserved for replenishment.

When taking out old material, it should be composted or stored on a safe site for several months toensure that undesirable bacteria and parasites die before using it between plants. Localregulations may dictate a controlled composting system, usually off site at a licenced facility, toeliminate the risk of zoonotic diseases being spread. For this reason some zoos segregateprimate, feline, canine, and carnivore waste and bedding and send it for controlled compostingthat guarantees 70°C for several days. Such requirements are listed as a condition within somezoo licences.

Dry mulch creates dust. Mulch should be kept moist all the time to prevent dust and to enablebiological activity. It may be sufficient to spray water occasionally by hand once a week, dependingon the indoor humidity. An overhead irrigation mist system may be necessary on a large area, butcare must be taken to keep it well away from electric fittings etc. When mulch is moist it releasesacid and creates and an acid environment in the soil.

The mulch is grounded down by the mechanical activity of the animals‘ feet and degrades tohumus, absorbs water and develops the desirable biological activity that decomposes urine andfaeces. Under good conditions, the lower layer should maintain itself and should not be disturbed.However, deep mulch should be regularly monitored for sufficient moisture and eventual mildew bydigging down.

When using dead wood and trunks in the enclosure, fungi can develop, particularly shortly afterinstallation.

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Photo 4: Cutting out concrete flooring for replacement by sand© Jonas Homburg, 2017


Disinfection is not recommended, except for quicklime or slaked lime that can develop hightemperatures when in contact with water. It is better to take mulch with fungi out and spread it onthe ground until the biological balance is re-established.

Bark with high levels of tanning agents create acid conditions in the soil when kept moist. Theseare desirable conditions for keeping fungi growth down and decomposing activity up.

Deep mulch can be refreshed once or twice a year by flooding the area or by using a sprinklersystem to thoroughly soak the substrate to the point of saturation. The flood and drain option canalso be used to cleanse the material from pest infestations. Good drainage is essential in anycase.

5. Case studies

5.1 Primates

At Frankfurt Zoo, mulch bedding has been used for decades in renovated ape and monkeyenclosures in the Monkey House before the new Bogori ape house opened in 2008 with bio-floors.

Mulch bedding with fifty centimetres minimum depth has been kept for many years without theneed of being totally exchanged. Mulch that is lost by cleaning and by decay into humus isreplenished. A year after installation of the mulch bedding, wood chips from tanning species (oak,evergreens) have been added. Wood chips are not as comfortably soft and do not hold as muchwater, but decay slower and aerate better than mulch.

The indoor exhibits for apes at Zoo Frankfurt have a concrete base and a drainage system. Thebio-floor is a soil-mix with mulch on top that allows plant growth in places that are not compactedby the apes. Faeces is collected and mulch replenished.

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Photo 5: Gorillas at Frankfurt Zoo© Monika Fiby, 2009


Lincoln Park‘s Kwan Gorilla exhibit opened in 2004 with a one metre deep bio-floor from woodchips on a concrete base. Keepers water it occasionally and turn the top layer over every twoweeks to aerate the system.

Deep mulch of sixty centimetres depth is used in primate enclosures at Heidelberg Zoo. The mulchis a little aerated when exchanging straw and watered every second day depending on theweather. When the bedding degrades to thirty centimetres depth it is replenished, but almostnever replaced.

Planckendael Zoo installed an 80cm mulch bedding on drainage mats in its new bonobo indoorquarters.

Dublin Zoo has several methods in use. Chimpanzee enclosures have a tree surgeons chippingsdeep bed of about twentyfive centimetres that was not fully changed for many years. Badly soiledareas are cleaned, old surrounding bark is pulled in, and the surface is topped up as needed.There have not been any rodent issues, but occasionally too many slugs, although using sawdustin wet areas seems to reduce this problem.

Gorillas and many smaller primate enclosures have softwood chips bedding without any bark,twigs, or leaves at all, only white wood. This has been found to last much longer than treesurgeons chippings. Because of is porousness, it harbours less woodlice or slugs, shows lessfungal growth, needs less depth, and much less frequent cleaning. It thereby requires less stafftime and causes less waste costs.

Osnabrueck Zoo built its winter quarters for chimpanzees on strip foundations. The natural soil isused for sub-tropical plants that are sprinkled automatically. The chimpanzees are living in thegreenhouse only in winter. Plants recover during summer when the chimpanzees are outdoors.

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Photo 6: Gorillas at Dublin Zoo © Monika Fiby, 2018


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Photo 7: Osnabrueck Zoo, chimpanzees on bio-floor by end of winter© Jonas Homburg, 2014

Photo 8: Osnabrueck Zoo, chimpanzee winter quarters by end of summer© Jonas Homburg, 2014


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Photo 9: Lion exhibit at Frankfurt Zoo© Jonas Homburg, 2013

Photo 10: Tiger exhibit at Frankfurt Zoo© Monika Fiby, 2006


5.2 Big Cats

The indoor exhibits for big cats at Zoo Frankfurt are built without a concrete base, but on stripfoundations with natural ground that is covered with mulch or sand, depending on the species. Thebio-floor breaks down urin. Faeces is collected and mulch replenished. Mulch in the tiger exhibitturns into humus that is useful for the plants in the exhibits.

Existing exhibits at Heidelberg Zoo were adapted to use deep mulch. You can learn more aboutthis Sumatran Tiger exhibit in the ZooLex Gallery at www.zoolex.org.

Because of constraints indoors from tiled floor and low doors, the depth is limited to 40cm. Thecats are using these enclosures every night. Once a day, the bedding is cleaned from faeces andaerated with a ripper to a depth of ten to twenty centimetres. Once a year the bedding isreplenished. It is totally exchanged every second year. There is a nice smell of bark and forest inthis otherwise traditional cat house.

5.3 Herbivores

While it has been normal to keep elephants on sandy soil outdoors, sand has slowly found its wayinto buildings. Today, it has become normal to install sandy soil in elephant indoor quarters too.

Kaziranga Forest Trail at Dublin Zoo opened 2007. Bunker sand for golf courses is used for theflooring because it has graded large size particles with excellent drainage properties and does notbed down. The surface sand is loosened every day and mounded by staff. Drains along theconcrete base take excess water to the sewer. All urine very quickly disappears. Mist units areused to keep the sand surface moist when it gets too dusty. Some sand is removed when cleaningmanure out and is occasionally replenished – about every three months at Dublin Zoo. The naturalbiological activity within the sand prevents smells. Natural UV through skylights assists with urinebreakdown.

One and more metres of sand is used in the Elephant House that opened at Copenhagen Zoo in2008.

At Heidelberg Zoo, no concrete foundation was built for the elephant house in 2010. Severalmetres of sand are laying on natural soil in the elephant hall and stalls. Two stalls that can be usedfor medical treatment have rubber floor. You can learn more about this Asian Elephant exhibit inthe ZooLex Gallery at www.zoolex.org.

Magdeburg Zoo and Blair Drummond Safari keep their rhinoceroses on sand bio-floor.

When indoors, okapis at Rotterdam Zoo are lin a greenhouse with a mix of soil and vulcanicsubstrate on the ground.

At Magdeburg Zoo, Tapirs are living on a mulch and black rhinos on a sandy loam bio-floorinstallation on concrete plate foundations.

At Dublin Zoo, mulch was chosen for the giraffe house because it is easier to clean from smalldroppings than sand. Bark and wood chips create a stable surface inside for the giraffes that weartheir hooves on the sandy surface outside. The giraffe house floor slopes to drains in the centre.About 30 centimetres of tree surgeons chips minimum are piled around edges and about a metrein middle.

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Photo 12: Elephants on sand bio-floor at Copenhagen Zoo© Monika Fiby, 2017

Photo 11: Elephants on sand bio-floor at Dublin Zoo© Monika Fiby, 2018


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Photo 13: Elephants on sand bio-floor at Heidelberg Zoo© Jonas Homburg, 2017

Photo 14: Magdeburg Zoo, black rhinoceros on loamy sand© Jonas Homburg, 2014


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Photo 16: Magdeburg Zoo, tapirs on deep mulch © Jonas Homburg, 2014

Photo 15: Rotterdam Zoo, okapis on bio-floor© Jonas Homburg, 2019


5.4 Birds, reptiles, amphibia

Mulch is used in enclosures for birds and reptiles at Zoo Frankfurt. The quality is the same as isused for horticulture purposes.

Bark of oak and chestnut has high levels of tanning agents. Bark of evergreen trees such as pinesadditionally carries essential oils. Both, tanning agents and essential oils can be hazardous forreptiles, that swallow mulch parts with their food. Such mulch can also irritate amphibia's skin.

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Photo 17: Trumpeter bird exhibit at Frankfurt Zoo© Jonas Homburg, 2013


6. Development

We hope that the above mentioned examples encourage to plan for and install bio-floors inrenovated and new indoor animal enclosures.

While the focus of this article is on indoor enclosures it should be common practice to provide soilwith biological activity in outdoor enclosures, except for heavily used and feeding areas. Theprinciples of aeration, humidity and drainage for biological activity are the same as indoors, buttechnologies may differ a lot, depending on climatic conditions and species' needs.

We look forward to receiving and disseminating information about your bio-floor projects.

Contact: [email protected]

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Photo 18: Sunbittern exhibit at Frankfurt Zoo© Jonas Homburg, 2013

bio-floors in animal enclosures 14 may 2020€¦ · 14/05/2020 · introduction 1.1 definition...

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