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Recommendations for construction of the cage itself

Surroundings and construction details for cages
Slender loris cages must be located in a reasonably quiet place; a cover on the cage fronts with small holes for observation can reduce stress when necessary. Smell of nearby conspecifics did not cause any recognizable signs of social stress in the colony at Ruhr-University since the animals were used to it, but in the first months after import, there was some evidence of social stress by olfactory causes even in animals housed solitary (Schulze & Meier, 1995).
Two adjacent cages connected by a passage or shutter are better than one large cage because they provide possibilities to separate animals without distress when necessary, and they allow cleaning without animals inside the cage. The following table shows effects of different kinds of separation between animals.
The table above gives some recommendations for minimum cage size, but much larger cage systems are completely used, and field studies indicate that territories in the wild may be much larger than previously expected (F. Wiens, A. Nekaris, pers. comm.). Insufficient cage size or insufficient availability of space because of lack of branches in the cage seem to increase the risk of fighting between animals (Rasmussen, 1986; Fitch-Snyder et al., 2001).

Figure: system of two adjacent cages recommended for lorises


Table 1: recommendations for minimum cage size
  Minimum cage height Minimum cage size*¹ Minimum base   Minimum amount of branches
Fitch-Snyder et al., in preparation 2.5 m 16 m³ 6.25 m² 2.5 x 2.5 m  
Recommended minimum (Bochum University) 2-2.5 m For Loris: 2,5 m³ *²  1 m² 1 x 1 m 15 m *³ 
Official German guideline for mammals, 1996  2 m 1,5 m³   1 x 0.75 m  

*¹ As lorises do not jump, only the parts of cage furnished by branches can be used. Empty space which is not available for the animals therefore should not be considered when cage size is judged.

*² (Cage size only sufficient in connection with very good cage furnishing and some behavioural enrichment, for instance free access to a separate play room at times and / or passages allowing running and looking outside the cage.

*3 including several m of horizontal branches, firmly attached, in the upper part of the cage

Effect of separating cage elements on the behaviour of adult slender lorises of equal and of opposite sex, unfamiliar to each other (Data based on routine observation, additional tests of 30 minutes duration and limb measurements of dead animals).

Table 2: effects of different types of separationg cage walls
Separation by wall type:  Behaviour observed when a conspecific is noticed behind the wall: Possible risks
Solid wall, no optical contact Influence by acoustic stimuli. Some evidence of effects of olfactory stimuli No risk caused by the wall. Territorial whistles of neighbours may cause aggressive behaviour
Solid wall with narrow clefts, no optical contact, but smell of neighbours perceivable through clefts Sniffing at clefts and attempts to push the hands through clefts have occured. In rare cases, aggressive behaviour on both sides of a cleft occurred when neighbours noticed the smell and noise of such attempts. If clefts are broad enough, a hand may be pushed though and bitten. One animal got trapped, unable to pull its hand back, and lost a finger because of repeated bites by neighbours.
Glass Initially confusion, signs of social stress or not, sniffing at the edge of the glass. As an exception, initial low intensity threat occurred. In the long run: some interest in activities of neighbours on the other side of the glass, but no signs of agonistic behaviour. No risk by agonistic behaviour known. In one case, an animal initially tried to bridge over to branches behind the glass, hit the glass, almost fell down and showed signs of distress and confusion for several minutes afterwards.
(Mirror: own image instead of conspecific)
Signs of social stress or not, curiosity. 
No aggressive behaviour observed.
No risk known
Wiremesh allowing both optical and olfactory contact: Fierce defense of the territory against adults of the same sex may occur. Pushing against or through the wire with the hand(s) as an aggressive threat, attacks, territorial whistling, attempts to bite the opponent´s hands. Fighting against neighbours and agonistic / territorial vocalization may cause aggression within groups in all cages. Danger of lesions: see further below. 
Single layer of fine wire-mesh, mesh size less than 3 mm
  Fierce agonistic behaviour, social stress; no bite wounds.
Single layer of wire-mesh, mesh size 3 mm or more
Animals may cling to the wiremesh while fiercely attacking each other if mesh width is larger than finger diameter (see figure) Heavily bleeding bite wounds inflicted to fingers and toes
Single layer of wire-mesh, mesh size 1 cm x 1.5 cm or more
  Bite wounds; hands pushed through the meshes may be seized and repeatedly bitten by the inhabitants of the next cage. In larger meshes (2.5 x 2.5 cm), animals may jam themselves; see figure.
2 wiremesh layers, 2 cm apart.
  Fine wiremesh: no lesions. Coarse wiremesh: the hand or arm may be pushed through (see figure) and bitten by the inhabitants of the next cage. 
2 wiremesh layers, 20 cm apart
No problems observed in the colony at Ruhr-University. In animals not habituated to the presence of many conspecifics, reactions might be different. ?

In general, observation shows that a combination of olfactory and optical stimuli from nearby conspecifics may lead to severe aggressive behaviour whereas similar perception of other species including humans has no such effect. Therefore, if an animal behaves friendly towards the keeper, this does not allow any conclusion about friendliness towards conspecifics. This must be considered when potential mates are introduced to each other: initial tests with a safe double wiremesh wall may help to avoid trouble. Smell alone or agonistic vocalization apparently can cause some aggression, but with a limited effect, optical stimuli alone apparently cause little or no aggression.

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Slender loris husbandry information
H. Schulze, Ruhr-University Bochum Last amendment: 24 February 2001
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