Species keeper protocol

Cyclura lewisi

Grand Cayman Blue Iguana
An Endangered Grand Cayman endemic. Maintain intense basking and UV, a plant-dominant diet, large terrestrial space with secure retreats, a milder dry season November-April and increased rain from mid-May through October. Breeding is usually spring to early summer, followed by June-July nesting.

Day air28-31 CSeasonal ambient target with cooler retreats

Basking surface42-46 CBroad local basking zone; not whole-enclosure air

UVI under T5UVI 4-6At normal back height; covered refuges near UVI 0

SeasonLate hatching; juvenile growthMain mating April-May / early June; laying usually June-July

Keeper timer setting

T5 UVB: one hour later on, one hour earlier off

ON: 1 hour after the daylight lights come on.
OFF: 1 hour before the daylight lights go off.

October: daylight 11.7 h; T5 UVB 9 h 42 m per day.

The T5 runs for two hours less than the total photoperiod. Example: daylight 08:00-20:00 means UVB 09:00-19:00. Keep the monthly UVI strength as listed beneath the tube. Existing care values are preserved.

UVI beneath the optional T5 tube

Working exposure target

October target at normal back height

UVI 4-6directly under the tube when it is on

Replace the blanket UVI 5-7 default with an optional adult T5 patch at UVI 4-6, aiming initially around 5. This is a moderate working choice within published exposure guidance, not proof that 5-7 is harmful or a measured optimum for every Cyclura. Published UV-Tool assignments vary even within the genus; no trial was found that makes UVI 7 a necessary default.

Your measuring point

Measure at the animal's normal back height directly beneath the brightest accessible part of the T5 strip, positioned toward the middle/back. The animal can enter and leave this area freely.

Keep a lower-UVI gradient and fully covered refuges near UVI 0. This is the optional exposure area, not the average across the cage.

Use a UV Index meter, such as a Solarmeter 6.5/6.5R. Warm the tube for about 30 minutes; keep reflector, guards and mesh in place. Raise or lower the fixture within its manufacturer's minimum-distance guidance, then recheck the reading and every higher accessible surface.

Evidence level: Inferred genus-level working range. These are working recommendations, often inferred; exact species optima and seasonal UV dose usually have not been measured. Log lamp-on time and animal behaviour as well as UVI.

Baines et al. (2016), UV-Tool · Muryn, Baines and Dishman (2026), Reptile Lighting Guide V10

October management

Selected automatically using the Netherlands date

Late hatching; juvenile growth

Grand Cayman - xerophytic shrubland, dry forest edge, limestone and rock-hole retreat habitat

28-31 CDay air

24-26 CNight

42-46 CBasking

4-6T5 UVI*

11.7 hPhotoperiod

9 h 42 mT5 UVB duration

69-82 / 80-90%RH day / night*

Wet season peak/transitionRain / mist

6Food days/week

Annual schedule

Scroll sideways on smaller screens

Month	Day air	Night	Basking	T5 UVI*	Photoperiod	T5 UVB duration	RH day / night*	Rain / mist	Food days/week	Seasonal management
January	25-28 C	21-23 C	41-45 C	4-6	11.1 h	9 h 6 m	58-70 / 70-80%	Dry season; light AM mist 2-3x/wk	5	Cooler dry-season maintenance; maintain body condition
February	25-28 C	21-23 C	41-45 C	4-6	11.5 h	9 h 30 m	57-69 / 70-80%	Dry; localized humid retreat	5	Condition breeders; gradual activity increase
March	26-29 C	22-24 C	42-46 C	4-6	12.0 h	10 h	56-69 / 70-80%	Driest month; avoid chronic wetness	5-6	Courtship may begin early in some years
April	27-30 C	23-25 C	42-46 C	4-6	12.5 h	10 h 30 m	60-72 / 72-82%	Dry-to-wet transition; rain pulses increase	6	Breeding activity rising; prepare nest areas
May	28-31 C	24-26 C	43-47 C	4-6	12.9 h	10 h 54 m	64-76 / 76-86%	Wet season begins; regular rain pulses	6-7	Main courtship and mating period
June	29-32 C	25-27 C	43-47 C	4-6	13.1 h	11 h 6 m	66-78 / 78-88%	Warm wet season	6-7	Late mating; gravid females; nesting starts
July	29-32 C	25-27 C	43-47 C	4-6	13.0 h	11 h	67-80 / 79-89%	Wet; frequent showers	6-7	Main oviposition window; guard nest zones
August	29-32 C	25-27 C	43-47 C	4-6	12.7 h	10 h 42 m	68-81 / 80-90%	Wet/storm season	6	Incubation; female recovery
September	29-31 C	25-27 C	42-46 C	4-6	12.2 h	10 h 12 m	69-82 / 80-90%	Wet; high rainfall/hurricane risk	6	Incubation and early hatching possible
October	28-31 C	24-26 C	42-46 C	4-6	11.7 h	9 h 42 m	69-82 / 80-90%	Wet season peak/transition	6	Late hatching; juvenile growth
November	27-30 C	23-25 C	41-45 C	4-6	11.3 h	9 h 18 m	64-77 / 75-86%	Rainfall easing	5-6	Transition to dry season; reduce rain gradually
December	26-29 C	22-24 C	41-45 C	4-6	11.0 h	9 h	60-73 / 72-82%	Dry-season transition	5	Seasonal reset; no cold brumation

Keeper notes

Use measured gradients and animal behaviour, not single thermostat readings

T5 UVI measurement

Measure UVI at normal back height directly beneath the brightest accessible part of the optional T5 strip. Place the strip toward the middle/back with free access to and away from it; preserve a gradient into fully covered refuges near UVI 0. These numbers describe the exposure area, not the whole enclosure or a daily average.

UVI review

Habitat

Grand Cayman endemic; surviving populations use xerophytic shrubland, dry-forest edges, limestone terrain and rock-hole retreats.

Climate

Grand Cayman has a warm tropical marine climate, with a wet season from mid-May through October and a milder dry season November-April.

Diet

Primarily herbivorous: browse, leafy weeds, flowers, cactus and fibrous vegetables should dominate; fruit and animal foods remain minor.

Breeding

Traditional mating is April-May into early June, but the conservation programme has documented unusually early mating in some recent years.

Nesting

Oviposition is usually June-July. Natural/captive guidance places the chamber base around 30 cm deep; provide a large compactable nest bank well before laying.

Incubation

IUCN husbandry guidance gives about 32 C for 66-80 days; broader zoo summaries report 30-33 C and roughly 60-90 days.

Status

Cyclura lewisi is Endangered on the IUCN Red List and CITES Appendix I.