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/source Plenty of inverts Submerged 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.