Habitat Suitability Index

Habitat Suitability Index

Evaluates (pond) habitat quality

10 suitability indices, all of which are factors known to

affect great crested newts

Combined index, between 0 and 1

– 0 indicates unsuitable habitat

– 1 optimal habitat

Ponds with higher index more likely to support great

crested newts

Data collection & calculation of HSI

• 10 factors are scored for the pond• Convert to SI scores ranging from 0.01- 1• (Do not give any SI score a value of 0)• The 10 scores are then multiplied together• The tenth root of this number is then calculated• The calculated habitat suitability index should be

between 1 and close to 0

• H S I = (SI1 x SI2 x SI3 x SI4 x SI5 x SI6 x SI7x SI8 x SI9 x SI10) ^(1/10)

Categorisation of HSI scores

HSI Pond suitability

<0.5 Poor

0.5- 0.59 Below average

0.6- 0.69 Average

0.7- 0.79 Good

>0.8 Excellent

Geographic Location (SI-1)

Geographic location (SI-1)

Pond Area (SI-2)

Pond Permanence (SI-3)

Water Quality (SI-4)

Water catchment/sourcePlenty of invertsSubmerged vegetation

Don’t confuse water clarity with quality

Water Quality

Category SI Criteria

Good 1.0 Abundant & diverse communities Netting = diverse inverts including mayfly larvae & water shrimps

Moderate 0.67 Moderate invert diversity

Poor 0.33 Low invert diversity (e.g.species such as midge and mosquito larvae), few submerged plants

Bad 0.01 Clearly polluted, only pollution tolerant species (rat-tailed maggots), no submerged plants

Shading (SI-5)

• Estimate the % of perimeter shaded (usually by trees)

• Include trees that cast a shade to at least 1m from shore

• Does not include emergent vegetation

• Make estimate in May- end of Sept

Shading (SI-5)

Heavily shaded ponds less likely to support great crested newt

Waterfowl (SI-6)

Impacts waterfowl have on ponds and newts:• Remove aquatic vegetation• Pollute water• Stir up sediments• Some waterfowl actively hunt adult newts and

larvae

Fish (SI 7)

Fish (SI 7)

Category SI Criteria

Absent 1 Absent

Possible 0.67 Possible

Minor 0.33 Minor (Crucian Carp & sticklebacks)

Major 0.01 Major (other species or carp/sticklebacks in dense populations)

Pond Count (density) (SI-8)

Higher pond densities – more likely to support great crested newt

Terrestrial Habitat (SI-9)

• Good terrestrial habitat offers- cover, foraging opportunities

• Habitat includes meadow, rough grassland, hedges, scrub, woodland and gardens

Category SI Criteria

Good 1 Extensive area of habitat offering good areas for foraging and shelter. > 75% of available area

Moderate 0.67 Habitat offers opportunities for foraging and shelter. 25-75% of available area

Poor 0.33 Habitat offers little opportunity for foraging and shelter< 25% of area

None 0.01 No suitable habitat around the pond

Macrophyte cover (plants) (SI–10)

Specific pond types - water tanks

© Ben Driver

Specific pond types – garden ponds

© Ben Driver

Flooded excavations

The largest newt populations are found in disused mineral sites (also clay and chalk pits)

References

• Oldham, R.S., Keeble, J., Swan M.J.S & Jeffcote M. (2000). Evaluating the suitability of habitat for the Great Crested Newt (Triturus cristatus). Herpetological Journal 10 (4), 143-155

Photographs

• Copyright of all photographs remains with the photographers and ARC.

• These photographs should not be used for purposes other than NARRS training without the permission of the photographers.