Amphibians: Manipulate larval density within the enclosure

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

88%
Certainty

28%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Some species of amphibian larvae are known to cannibalize other individuals in the enclosure if animal density is too high. It is also thought that growth could be reduced when larvae are too densely housed.

Study locations

Key messages

A replicated study in the USA found that reducing larval density of spotted salamanders increased larval survival and body mass.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated study in 2010 of spotted salamanders Ambystoma maculatum in the USA found that housing larvae at low densities resulted in bigger salamanders, higher survival and lower stress levels, similar to larvae in the wild. At different larval densities there were significant differences in body mass (6/tank: 1.8 g; 12/tank: 1.6 g; 30/tank: 0.9 g), survival (94%; 67%; 33% respectively) and stress levels (white blood cell ratios: 0.4; 1.5; 2.2 respectively). At medium larval densities, increased food or habitat complexity had no significant effect on body mass (food: 1.4 g; environment: 1.7 g), survival (89%; 50% respectively), or stress levels (1.3; 0.7 respectively). Egg masses were collected from the wild. Larvae were reared in three replicates of five treatments: starting densities of six, 12 or 30 larvae/1,000 l tank, increased food (12 larvae/tank with triple the zooplankton) or increased habitat complexity (tank filled with sticks and refugia). All tanks had leaf litter on the bottom. Metamorphs were weighed and blood sampled for stress hormone levels.
Study and other actions tested
Referenced paper
Davis A.K. (2012) Investigating the optimal rearing strategy for Ambystoma salamanders using a hematological stress index. Herpetological Conservation and Biology, 7, 95-100.

Please cite as:

Jonas, C.S., Timbrell, L.L., Young, F., Petrovan, S.O., Bowkett, A.E. & Smith, R.K. (2020) Management of Captive Animals. Pages 527-553 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Management of Captive Animals

Related Actions

Actions	Effectiveness	Studies	Category
Amphibians: Manipulate larval density within the enclosure Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Amphibians: Manipulate temperature of enclosure to improve development or survival to adulthood Action Link	Trade-off between benefit and harms	4	Synopsis Link
Amphibians: Allow adults to attend their eggs Action Link	No evidence found (no assessment)	0	Synopsis Link