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Similarly, Damaraland mole-rats have a dispersive morph made up of bigger mole-rats who do less work (Hazell et al. 2000, Scantlebury et al. 2006). Scantlebury et al. (2006) found that these mole-rats work little until after rains, when they substantially increase their work in comparison to normal workers. The disperser mole-rats are also significantly bigger than the queen, who is significantly larger than the workers (Scantlebury et al. 2006). The disperser morph in both species has an advantage that allows it to attempt the second strategy, dispersing and gaining direct reproduction. Its larger fat stores allow it to travel longer distances without starving and provide a good reserve of energy when beginning reproduction (Scantlebury et al. 2006). Overall, the disperser morph, while costly to its natal colony in terms of energy consumed and not used (O’Riain et al. 1996, Scantlebury et al. 2006), benefits itself through the potential for direct reproduction and provides gene flow for these highly unusual and fascinating mammalian species (Faulkes et al. 1997a).


The evolution of eusociality in mole-rats can be explained primarily by the Aridity Food Distribution Hypothesis which uses the environmental factors of aridity and unequal food distribution to explain why certain species of mole rats evolved to be eusocial. This also accounts for the separate evolution of eusociality in two different species. As a eusocial species, the mole-rat has tiers of breeders, workers, and dispersers. The situations in which mole-rats will and will not breed is not entirely understood, but appears to be more socially or hormonally driven, as even mole-rats who are not mole-rats do preserve their ability to reproduce, even if they do not use it. The dispersal tier of the mole-rat eusocial hierarchy is essential to allowing for enough outbreeding to sustain healthy offspring, and allows large, successful colonies to spread their genes even further. The entire hierarchy of eusociality in mole-rats is certainly intricately evolved, from intrinsic differences to social cues that allow the mole-rat to survive in harsh conditions.

Discussion questions

  1. In mole-rats, non-breeders do not lose reproductive capabilities. If non-breeder tiers of the mole rat did engage in reproductive behavior, how might this interfere with the eusocial structure of the colony? Would this behavior increase that individual’s fitness, why or why not?
  2. Eusociality appears to have evolved twice separately in the mole-rat. What conditions would likely allow for eusocial evolution in other mole-rat species, or even in other organisms that are typically solitary?


  • Arid climate - characterized by severe lack of available water
  • Basal clade - the first to diverge from the lineage in a cladogram
  • Dimorphism - two distinct body forms of an individual within a species
  • Eusocial - applies to a society with reproductive division of labor, overlapping generations, and cooperative care of young
  • Fractal dimension - the extent that the burrow fills the area it inhabits
  • Fitness - ability of an individual to stay alive and pass on genes
  • Inbreeding - breeding with relatives, leads to less genetic variation
  • Inbreeding depression - a decrease in offspring size, fertility, and fitness due to inbreeding as recessive deleterious traits are more likely to manifest themselves in homozygous individuals
  • Inclusive fitness - the combination of direct fitness and indirect fitness gained
  • Indirect fitness - the fitness gained by helping a relative and impacted by the degree of relatedness
  • Kin Selection - altruistic acts directed towards kin that lead to greater overall inclusive fitness because of an increase in indirect fitness
  • Mesic - having a moderate supply of moisture.
  • Shoving - nose-to-nose pushing for protracted periods of time
  • Outbreeding - reproduction between two different populations , leading to more genetic variation
  • Reproductive skew - distribution of breeding between members of a population where some members hold more breeding rights than others


  • Alexander RD, Noonan KM, Crespi BJ. 1991. The evolution of eusociality. In: Sherman PW, Jarvis JUM, Alexander RD. The Biology of the Naked Mole Rat. Princeton (NJ): Princeton University Press. p. 3-44.
  • Allard MW, Honeycutt RL. 1992. Nucleotide sequence variation in the mitochondrial 12S rRNA gene and the phylogeny of African mole-rats (Rodentia: Bathyergidae). Mol Biol Evol. 9:27–40.
  • Braude S. 2000. Dispersal and new colony formation in wild naked mole-rats: evidence against inbreeding as the system of mating. Behav Ecol. 11:7–12.
  • Burda H. 1995. Individual recognition and incest avoidance in eusocial common mole-rats rather than reproductive suppression by parents. Experientia. 51:411–413.
  • Burland TM, Bennett NC, Jarvis JUM, Faulkes CG. 2002. Eusociality in African mole-rats: new insights from patterns of genetic relatedness in the Damaraland mole-rat (Cryptomys damarensis). Proc R Soc Lond B. 269:1025-1030.
  • Burland TM, Bennett NC, Jarvis JUM, Faulkes CG. 2004. Colony structure and parentage in wild colonies of cooperatively breeding Damaraland mole-rats suggest incest avoidance alone may not maintain reproductive skew. Mol Ecol. 13:2371-2379.
  • Ciszek D. 2000. New colony formation in the “highly inbred” eusocial mole-rat: outbreeding is preferred. Behavioral Ecology. 11:1-6.
  • Clarke FM, Faulkes CG. 1999. Kin discrimination and female mate choice in the naked mole-rat Heterocephalus glaber. Proc R Soc Lond B. 266:1995-2002.
  • Faulkes CG, Abbott DH. 1993. Evidence that primer pheromones do not cause social suppression of reproduction in male and female naked mole-rats (Heterocephalus glaber). J Reprod Fert. 99:225-230
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About the author

A portrait of the author.

Sheena Shah-Simpson is an undergraduate from Arlington, Texas, majoring in Biochemistry and Cell Biology. In her free time she likes to play, or attempt to play, musical instruments, read, hang out with her friends, listen to good music, and dance. While studying animal behavior she learned fascinating things about conflicts of interest, between species, within species, within individual families (parent-offspring conflict is particularly interesting), etcetera. Writing this chapter, Sheena also learned many extraordinary things about such varied topics as incest and different morphologies within just one family of animals, the ever-fascinating mole-rats.

Questions & Answers

What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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Damian Reply
absolutely yes
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s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Mockingbird tales: readings in animal behavior. OpenStax CNX. Jan 12, 2011 Download for free at http://cnx.org/content/col11211/1.5
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