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Naked Mole-rat (Heterocephalus glaber) Fact Sheet: Reproduction & Development

Reproduction

Sexual maturity

  • As early as 7 to 9 months, when not sociologically suppressed (see next section) (Jarvis 1991; Patterson 2016)
    • Minimal development of reproductive structures in nonbreeding individuals (Jarvis and Sherman 2002)

Breeding system

  • Breeding restricted to 1 dominant female (“queen”) and 1 to 3 breeding males (Jarvis 1981; Brett 1991b; Jarvis 1991; Faulkes, Abbott, O’Brien, et al. 1997; Maree and Faulkes 2016; Patterson 2016)
    • Reproduction is behaviorally and hormonally suppressed in other colony members (in both sexes) (Faulkes, Abbott, Jarvis, et al. 1990; Faulkes et al. 1991; Faulkes and Abbott 1991; Faulkes et al. 1994; Smith et al. 1997; van der Westhuizen et al. 2006; Bennett et al. 2018)
  • Queen is the largest and most aggressive of the females (Brett 1991b; Reeve and Sherman 1991; Patterson 2016, and as noted)
    • May hold highest status for 16 years or more
    • Queen’s shoving behavior suppresses ovulation in other females (Margulis et al. 1995)
  • Queen selects 1 to 3 males to breed with—often oldest, largest, and more distantly related males in colony (Clarke and Faulkes 1999; Braude 2000; Ciszek 2000; Patterson 2016, except as noted)
    • Mating usually occurs 7 to 10 days after birth of previous litter (Lacey and Sherman 1991)
    • Estrus period: 24 h or less (Lacey et al. 1991; Lacey and Sherman 1991)
    • When ready to mate, queen solicits one or more males by backing up and presenting her hindquarters (Lacey et al. 1991)
      • Copulation short, typically about 15 sec
    • Each litter may have 2 to 3 sires (multiple paternity) (Faulkes, Abbott, et al. 1997)
      • Appear to prefer less-familiar males but inbreeding common
  • Nonbreeding colony members cooperatively care for young (alloparenting) (Jarvis 1991)
  • Queen may breed until advanced age (21 years) (Jarvis and Sherman 2002)
  • Within days of queen’s death, a few of the highest ranking females begin ovarian cycling (Clarke and Faulkes 1997; Smith et al. 1997)
    • Aggressively fight
    • Most aggressive female becomes queen

Sperm structure

  • Unusual spermatozoa structure (van der Horst et al. 2011)
    • Different than most mammals­—probably because little to no competition with other males

Gestation and Birth

Gestation

  • Gestation period (Lacey and Sherman 1991; Roellig et al. 2011; Maree and Faulkes 2016; Patterson 2016)
    • About 70 days (range: 66 to 74 days)
      • Twice as long as other rodents of similar size
    • Subordinates feed and care for queen during gestation
  • Changes to queen’s body during pregnancy (O’Riain et al. 2000; Patterson 2016)
    • During first few pregnancies, queen’s spine becomes longer and abdomen becomes larger
      • Larger body cavity to carry larger litters
    • Body mass may increase by more than 80% in advanced pregnancy
  • Subordinates feed and care for queen during gestation (Jarvis 1991)
  • Nipples enlarge in nonreproductive colony members of both sexes (Jarvis 1991)
    • Do not produce milk

Birth

  • Litter size
    • Queen gives birth to 11 to 12 young, on average (range: 1 to 28) (Sherman et al. 1999; Maree and Faulkes 2016; Patterson 2016)
      • Some authors report about 5 to 9 young (e.g., Lacey and Sherman 1991) or 14 young (Braude 1991), on average
  • Weight at birth
    • 1 to 2 g (0.04 to 0.07 oz) (Brett 1991b; Jarvis 1991; Urison and Buffenstein 1995)
  • Interbirth interval
    • 76 to 95 days (Jarvis 1981; Brett 1991b; Jarvis 1991; Urison and Buffenstein 1995)
      • May be longer in managed care (Roellig et al. 2011)
    • Queen gives birth to 4 to 5 liters (50 or more young) per year (Lacey and Sherman 1991)
  • Queen active during birthing period (Jarvis 1991; Lacey et al. 1991)
    • Labor lasts 1 to 3 h
    • Behaviors
      • Runs in tunnels
      • Nudges and licks genital area
      • May reach around and gently remove pup with teeth
    • Young born in tunnel or nest chamber
  • Queen receives little assistance from subordinates during birth (Jarvis 1991)
    • Exception: Subordinate caregivers may clean pups and carry them to the nest (Lacey et al. 1991)

Parental Care

Care of young

  • Younger, smaller nonbreeding colony members feed and attend to queen and young (Patterson 2016)
    • Caregivers may be from recent litters
  • Caregivers groom young and keep them warm (Jarvis 1991; Patterson 2016)
    • Also keep young from moving too far
      • Young carried between incisors
  • Pups form part of general huddle in nest (Jarvis 1991)
  • When queen enters nest chamber, pups move towards her; queen does not seek out pups (Jarvis 1991)
  • Subordinates’s caregiving behavior induced by hormones absorbed through ingestion of queen’s feces (Watarai et al. 2018)

Nourishment of young

  • Lactation period
    • 3 to 5 weeks (Lacey et al. 1991; O’Riain 1996; Patterson 2016)
  • Only queen nurses young (Jarvis 1991; Lacey et al. 1991)
    • Teats accessible to pups when queen lays on her back or side

Life Stages

Newborn

  • First 24 hours (Jarvis 1991; O’Riain 1996)
    • Young born bright red with transparent, gelatinous-like skin
      • Internal organs visible
    • Pups able to crawl and walk within hours of birth
    • Tips of incisors break through gums
    • Rely on senses of hearing and smell (e.g., to locate mother to nurse)
  • 1 to 2 weeks old (Porter 1957; Jarvis 1991; O’Riain 1996, except as noted)
    • Skin becomes more opaque
    • Claws develop
    • Show more interest in solid food
    • Begin to beg for feces from juveniles and adults
      • Vocalize and tug skin around provider’s anus
      • Gain nutrients and likely beneficial digestive microbes
    • Do not leave nest until at least 2 weeks of age (Braude 1991)

Juvenile

  • 3 to 8 weeks old
    • Eyes open (timing variable) (Jarvis 1991; O’Riain 1996; Chris Faulkes, personal communication, 2019)
    • Suckle less frequently (Jarvis 1991)
      • Continue to beg for feces
    • Weaning occurs (Jarvis 1991)
    • Gain mobility by 3 weeks; able to move quickly (O’Riain 1996)
  • After weaning
    • Young begin assisting with food transport, burrow maintenance, and raising the next litter (Jarvis 1991; Patterson 2016)
  • 3 weeks to 2 years
    • Pups and young adults spar with each other (Jarvis 1991; Jarvis and Sherman 2002)

Longevity

Long-lived rodent

(O’Connor et al. 2002; Sherman and Jarvis 2002)

  • Wild populations (AnAge 2019)
    • Nonbreeders: typically 2 to 3 years
    • Breeders: up to 17 years
  • Managed care
    • Over 30 years (Lewis and Buffenstein 2016; Ruby et al. 2017; AnAge 2019)
  • Good health maintained into late adulthood (O’Connor et al. 2002; Edrey et al. 2011)

Mortality and Health

Survival trends

  • Mortality of newborns/young can be high, especially during first week after birth (Braude 1991; Jarvis 1991; O’Riain 1996)
    • Typically caused by repeated moving by adults
      • Stressed by disturbance

Predators

  • Predators
    • Snakes (Brett 1991b)
      • Enter burrows
    • Raptors (Hill et al. 1957; Patterson 2016)
    • Owls (Hill et al. 1957; Patterson 2016)
  • Naked mole-rats susceptible to predation aboveground due to poor vision and hearing (e.g., Braude 1991; Patterson 2016)

Parasites (non-comprehensive list)

  • Mites (Lacey et al. 1991)
  • Chiggers (Lacey et al. 1991)

Cooperative Caregiving

Adult naked mole-rat carries young in mouth

Caregivers keep young warm and carry them back to the nest chamber if a newborn moves too far.

Caregivers are typically young, smaller colony members, which may be from recent litters.

Image credit: © San Diego Zoo Global. All rights reserved.

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