Here you’ll find the sources that informed Volume I of Mate: The Party Game for Feral Naturalists.
We drew from a delightful array of books, research papers, and field studies by scientists who have spent their careers documenting the rich, bizarre, and breathtaking world of animal mating behavior and anatomy.
What’s included here represents just a tiny sliver of the incredible work that exists. We hope to create many more volumes of Mate, and we warmly welcome inquiries from scientists, researchers, and fellow feral naturalists about our sources or about contributing to future editions.
| No. 1.001 | Schwartz, Steven K. et al. (2026). Males can benefit from sexual cannibalism facilitated by self-sacrifice. Current biology, 26(20), 2794-2799. |
| No. 1.002 | Yoshizawa, K., Ferreira, R. L., Kamimura, Y., & Lienhard, C. (2014). Female penis, male vagina, and their correlated evolution in a cave insect. Current biology, 24(9), 1006–1010. |
| No. 1.003 | Međimurski horse (stallion) at MESAP 2015, Silverije, Wikimedia Commons, CC BY-SA 4.0 |
| No. 1.004 | Isakov N. (2022). Histocompatibility and Reproduction: Lessons from the Anglerfish. Life (Basel, Switzerland), 12(1), 113. |
| No. 1.005 | Dixson, Alan F. (2012). Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Humans. Oxford University Press. p. 364. |
| No. 1.006 | Luongo, C., Llamas-López, P.J., Garrappa, G. et al. (2023). Impact of inclusion of post-spermatic ejaculate fraction in boar seminal doses on sperm metabolism, quality, and interaction with uterine fluid. Scientific reports, 13, 15258. |
| No. 1.007 | Ogawa, K., & Miura, T. (2014). Aphid polyphenisms: trans-generational developmental regulation through viviparity. Frontiers in physiology, 5, 1. |
| No. 1.008 | Brennan, P.L.R. (2022). Bird genitalia. Current Biology, 32(20), R1061 – R1062. |
| No. 1.009 | Meuffels-Barkas, J., Wilsher, S., Allen, W. R. T., Ververs, C., & Lueders, I. (2023). Comparative reproduction of the female horse, elephant and rhinoceros: implications for advancing Assisted Reproductive Technologies (ART). Reproduction & fertility, 4(3), e230020. Advance online publication. |
| No. 1.010 | Mann, J. (2006). Establishing trust: Socio-sexual behaviour and the development of male–male bonds among Indian Ocean bottlenose dolphins. In V. Sommer & P. L. Vasey (Eds.), Homosexual behaviour in animals: An evolutionary perspective (pp. 107–130). Cambridge University Press. |
| No. 1.011 | Ostrich penis (Struthio camelus), Elke Brüser, Flügelschlag und Leisetreter, Wikimedia Commons, CC BY-SA 4.0 |
| No. 1.012 | Simon, M. (2015, September 25). Absurd Creature of the Week: This slug has such a big penis it has to mate upside down. Wired. |
| No. 1.013 | Levine, B. A., Schuett, G. W., & Booth, W. (2021). Exceptional long-term sperm storage by a female vertebrate. PloS one, 16(6), e0252049. |
| No. 1.014 | Voigt, C., & von Helversen, O. (1999). Storage and display of odour by male Saccopteryx bilineata (Chiroptera, Emballonuridae). Behavioral Ecology and Sociobiology, 47, 29–40. |
| No. 1.015 | Thorp, J. H., & O’Neill, B. J. (2015). Hexapoda—Introduction to insects and Collembola. In J. H. Thorp & D. C. Rogers (Eds.), Thorp and Covich’s freshwater invertebrates (4th ed., pp. 849–871). Academic Press. |
| No. 1.016 | Masonjones, H. D., & Lewis, S. M. (1996). Courtship Behavior in the Dwarf Seahorse, Hippocampus zosterae. Copeia, 1996(3), 634–640. |
| No. 1.017 | Wittmann, D. & Blochtein, Betina. (1995). Why males of leafcutter bees hold the females’ antennae with their front legs during mating. Apidologie, 26, 181-196. |
| No. 1.018 | Cattet, Marc. (1988). Abnormal Sexual Differentiation in Black Bears (Ursus americanus) and Brown Bears (Ursus arctos). Journal of Mammalogy, 69, 849. |
| No. 1.019 | CC0 Public Domain |
| No. 1.020 | Fenelon, J., Renfree, M., & Johnston, S. (2021, June 9). Solving the mystery of the four-headed echidna penis. Pursuit. |
| No. 1.021 | Wait, L. (2023, November 27). These bats use their oversized penis to mate in a unique way, researchers find. Elsevier Connect. |
| No. 1.022 | Leonard, J. L., Pearse, J. S., & Harper, A. B. (2002). Comparative reproductive biology of Ariolimax californicus and A. dolichophallus (Gastropoda; Stylommiatophora). Invertebrate Reproduction & Development, 41(1–3), 83–93. |
| No. 1.023 | Omura, H., Ohsumi, S., Nemoto, T., Nasu, K., & Kasuya, T. (n.d.). Black right whales in the North Pacific. Scientific Reports of the Whales Research Institute. |
| No. 1.024 | Kohda, M., Tanimura, M., Kikue‑Nakamura, M., & Yamagishi, S. (1995). Sperm drinking by female catfishes: A novel mode of insemination. Environmental Biology of Fishes, 42(1), 1–6. |
| No. 1.025 | Kelly, D. A. (2013). Penile anatomy and hypotheses of erectile function in the American alligator (Alligator mississippiensis): Muscular eversion and elastic retraction. The Anatomical Record, 296(3), 488–494. |
| No. 1.026 | Barberini, F., Correr, S., De Santis, F., & Motta, P. M. (1991). The epithelium of the rabbit vagina: a microtopographical study by light, transmission and scanning electron microscopy. Archives of histology and cytology, 54(4), 365–378. |
| No. 1.027 | Sexual swelling in female Hamadryas baboon, Mamoritai, Wikimedia Commons, CC BY-SA 2.0 |
| No. 1.028 | Aisenberg, A., Barrantes, G. & Eberhard, W. (2014). Hairy kisses: Tactile cheliceral courtship affects female mating decisions in Leucauge mariana (Araneae, Tetragnathidae). Behavioral Ecology and Sociobiology. 69. 313-323. |
| No. 1.029 | Bourke, D. (1998). An introduction to the unique reproductive physiology and breeding activity of SACs. In Proceedings of the International Alpaca Conference (Fremantle, WA). |
| No. 1.030 | National Science Foundation. (2013, February 13). Animal attraction: The many forms of monogamy in the animal kingdom. |
| No. 1.031 | Bagemihl, B. (1999). Biological Exuberance: Animal Homosexuality and Natural Diversity (Stone Wall Inn ed.). New York City: St. Martin’s Press. |
| No. 1.032 | McLennan, M. R., & van Dijk, K. (2021). Use of a novel human object as a masturbatory tool by a wild male chimpanzee at Bulindi, Uganda. Pan Africa News, 28(1), 8–11. |
| No. 1.033 | Welke, K. W., Zimmer, S. M., & Schneider, J. M. (2012). Conditional monogyny: Female quality predicts male faithfulness. Frontiers in Zoology, 9, 7. |
| No. 1.034 | Yato, T. O., & Motokawa, M. (2021). Comparative morphology of the male genitalia of Japanese Muroidea species. Mammal Study, 46(4), 269–278. |
| No. 1.035 | Brennan, P. L. R., Cowart, J. R., & Orbach, D. N. (2022). Evidence of a functional clitoris in dolphins. Current Biology, 32(1), R24–R26. |
| No. 1.036 | Male–male genital licking (Bonin flying foxes), Norimasa Sugita, Figshare, CC BY-SA 4.0 |
| No. 1.037 | Anzai, R. K., Eleuterio, N. F., de Oliveira Lima, T., Haddad Manfio, R., & Almeida‑Santos, S. M. de. (2023). Pelvic spur use during courtship and mating in the red-tailed boa Boa constrictor. The Herpetological Bulletin, 163, 35–36. |
| No. 1.038 | Shibukawa, K., Tran, D. D., & Tran, L. X. (2012). Phallostethus cuulong, a new species of priapiumfish (Actinopterygii: Atheriniformes: Phallostethidae) from the Vietnamese Mekong. Zootaxa, 3363, 45–51. |
| No. 1.039 | Clemente, C. J., Gaschk, J. L., Del Simone, K., & Wilson, R. S. (2023). Resting disparity in quoll semelparity: Examining the sex‑linked behaviours of wild roaming northern quolls (Dasyurus hallucatus) during breeding season. Royal Society Open Science, 10(2). |
| No. 1.040 | Wedell, N., Gage, M. J. G., & Parker, G. A. (2002). Sperm competition, male prudence and sperm-limited mating in insects. Trends in Ecology & Evolution, 17(7), 313–320. |
| No. 1.041 | San Diego Zoo Wildlife Alliance. (n.d.). African and Asian Lions (Panthera leo) fact sheet: Reproduction & development. International Environment Library Consortium. |
| No. 1.042 | Muddy Elephant, Justin Hall, Flickr, CC BY 2.0 |
| No. 1.043 | Morgan-Richards, M., Trewick, S.A. and Stringer, I.A.N. (2010), Geographic parthenogenesis and the common tea-tree stick insect of New Zealand. Molecular Ecology, 19, 1227-1238. |
| No. 1.044 | Eberhard, William & Gelhaus, Jon. (2009). Genitalic stridulation during copulation in a species of crane fly, Tipula (Bellardina) sp. (Diptera: Tipulidae). Revista de Biologia Tropical, 57, 251-256. |
| No. 1.045 | Hayssen, V. & Orr, T.J. (2017). Reproduction in Mammals: The Female Perspective. JHU Press. |
| No. 1.046 | Sex: when less means more. (2000). BMJ : British Medical Journal, 320(7237), 736. |
| No. 1.047 | Hawkins, C.E., Dallas, J.F., Fowler, P.A., Woodroffe, R., & Racey, P.A.. (2022). Transient nasculinization in the fossa, Cryptoprocta ferox (Carnivora, Viverridae), Biology of Reproduction, 66(3), 610–615. |
| No. 1.048 | Sekizawa, A., Seki, S., Tokuzato, M., Shiga, S., & Nakashima, Y. (2013). Disposable penis and its replenishment in a simultaneous hermaphrodite. Biology letters, 9(2), 20121150. |
| No. 1.049 | Retief, T.A., Bennett, N.C., Kinahan, A.A., & Bateman, P.W. (2013). Sexual selection and genital allometry in the Hottentot golden mole (Amblysomus hottentotus). Mammalian Biology, 78(5), 356-360. |
| No. 1.051 | Earthworms mating, Jackhynes, Wikimedia, CC0 Public Domain |
| No. 1.052 | Oberlender, G., Solis-Murgas, L., Zangeronimo, M., Silva, A., & Pereira, L. (2012). Influence of ejaculation time on sperm quality parameters in high-performance boars. Journal of Animal Science Advances, 2, 499–509. |
| No. 1.053 | C. Meslin, T.S. Cherwin, M.S. Plakke, J. Hill, B.S. Small, B.J. Goetz, C.W. Wheat, N.I. Morehouse, & N.L. Clark. (2017). Structural complexity and molecular heterogeneity of a butterfly ejaculate reflect a complex history of selection, Proc. Natl. Acad. Sci. U.S.A. 114 (27) E5406-E5413. |
| No. 1.054 | Gist, D. H., & Jones, J. M. (1987). Storage of sperm in the reptilian oviduct. Scanning microscopy, 1(4), 1839–1849. |
| No. 1.055 | Hunt, G. L., Jr, & Hunt, M. W. (1977). Female-Female Pairing in Western Gulls (Larus occidentalis) in Southern California. Science (New York, N.Y.), 196(4297), 1466–1467. |
| No. 1.056 | J. D. D. Bishop, A. J. Pemberton. (2006). The third way: spermcast mating in sessile marine invertebrates. Integrative and Comparative Biology, 46 (4), 398–406. |
| No. 1.057 | Smuts, Barbara. (2001). Encounters with animal Minds. Journal of Consciousness Studies, 8, 293-309. |
| No. 1.058 | Roughgarden, Joan (2004). Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press. |
| No. 1.059 | Pacific Whale Foundation. (2024). Humpback whale penis extrusion and mating. |
| No. 1.060 | Lewis, S., South, A., Burns, R. & Al-Wathiqui, N. (2011). Nuptial gifts. Current Biology, 21 (17), R644-R645. |
| No. 1.061 | Abe, H., Sato-Okoshi, W., Tanaka, M., Okoshi, K., Teramoto, W., Kondoh, T., Nishitani, G., & Endo, Y. (2014). Swimming behavior of the spoon worm Urechis unicinctus (Annelida, Echiura). Zoology, 117(3), 216–223. |
| No. 1.062 | Rattlesnake hemipenes, Tess Thornton, Wikimedia Commons, CC BY-SA 3.0 |
| No. 1.064 | CHIU, M.-C., HUANG, C.-G., WU, W.-J., & SHIAO, S.-F. (2015). Morphological allometry and intersexuality in horsehair-worm-infected mantids, Hierodula formosana (Mantodea: Mantidae). Parasitology, 142(8), 1130–1142. |
| No. 1.065 | Yuen, Q.W.H., Brook, F.M., Kinoshita, R.E. and Ying, M.T.C. (2009). Semen Collection and Ejaculate Characteristics in the Indo-Pacific Bottlenose Dolphin (Tursiops aduncus). Journal of Andrology, 30, 432-439. |
| No. 1.066 | Young, L. C., Zaun, B. J., & Vanderwerf, E. A. (2008). Successful same-sex pairing in Laysan albatross. Biology letters, 4(4), 323–325. |
| No. 1.067 | David Lack. (1940). Courtship feeding in birds, The Auk, 57(2), 169-178. |
| No. 1.068 | Moscovice, L. R., Surbeck, M., Fruth, B., Hohmann, G., Jaeggi, A. V., & Deschner, T. (2019). The cooperative sex: Sexual interactions among female bonobos are linked to increases in oxytocin, proximity and coalitions. Hormones and Behavior, 116. |
| No. 1.069 | Naish, D. (2012, June 20). The terrifying sex organs of male turtles. Gizmodo. |
| No. 1.070 | CC0 Public Domain |
| No. 1.072 | Bates, L. A., Handford, R., Lee, P. C., Njiraini, N., Poole, J. H., Sayialel, K., Sayialel, S., Moss, C. J., & Byrne, R. W. (2010). Why do African elephants (Loxodonta africana) simulate oestrus? An analysis of longitudinal data. PloS one, 5(4), e10052. |
| No. 1.073 | Neufeld, C. J., & Palmer, A. R. (2008). Precisely proportioned: intertidal barnacles alter penis form to suit coastal wave action. Biological sciences, 275(1638), 1081–1087. |
| No. 1.074 | Dewsbury, Donald A. (1972). Patterns of copulatory behavior in male mammals. Quarterly Review of Biology, 1-33. |
| No. 1.075 | Hyman, L. H., Wake, M. H. (1992). Hyman’s Comparative Vertebrate Anatomy. United Kingdom: University of Chicago Press. |
| No. 1.076 | J. Bro-Jørgensen. (2002). Overt female mate competition and preference for central males in a lekking antelope. Proceedings of the National Academy of Science U.S.A. 99 (14), 9290-9293. |
| No. 1.077 | Cooke, L. (2022). Bitch: On the female of the species. Basic Books. |
| No. 1.078 | Hemidactylus frenatus mating (ventral view), Basile Morin, Wikimedia Commons, CC BY 4.0 |
| No. 1.079 | Tan, M., Jones, G., Zhu, G., Ye, J., Hong, T., Zhou, S., Zhang, S., & Zhang, L. (2009). Fellatio by fruit bats prolongs copulation time. PloS one, 4(10), e7595. |
| No. 1.080 | Sueur, J., Mackie, D., & Windmill, J. F. C. (2011). So small, so loud: Extremely high sound pressure level from a pygmy aquatic insect (Corixidae, Micronectinae). PLoS ONE, 6(6), e21089. |
| No. 1.081 | Burger, M. (2010). Complex female genitalia indicate sperm dumping in armored goblin spiders (Arachnida, Araneae, Oonopidae). Zoology, 113(1), 19–32. |
| No. 1.082 | San Diego Zoo Wildlife Alliance. (2025). Hippopotamus (Hippopotamus amphibius) & pygmy hippopotamus (Choeropsis liberiensis) fact sheet: Reproduction & development. International Environment Library Consortium. |
| No. 1.083 | Douglas, P., & Moscovice, L. (2015). Pointing and pantomime in wild apes? Female bonobos use referential and iconic gestures to request genito-genital rubbing. Scientific Reports, 5, 13999. |
| No. 1.084 | Hsu, M. H., & Wu, W. J. (2001). Off-host observations of mating and postmating behaviors in the cat flea (Siphonaptera: Pulicidae). Journal of Medical Entomology, 38(3), 352–360. |
| No. 1.085 | McGrath C. (2022). Highlight: Cracking the Shell of the Mysterious Argonaut Octopus. Genome Biology and Evolution, 14(11), evac156. |
| No. 1.086 | Orthetrum pruinosum mating (dragonflies), Jeevan Jose, Wikimedia Commons, CC0 Public Domain |
| No. 1.087 | Gunst, N., Vasey, P. L., & Leca, J. B. (2018). Deer mates: A quantitative study of heterospecific sexual behaviors performed by Japanese macaques toward sika deer. Archives of Sexual Behavior, 47, 847–856. |
| No. 1.088 | Lod, T., & Lesbarr, D. (2004). Multiple paternity in Rana dalmatina, a monogamous territorial breeding anuran. Naturwissenschaften, 91(1), 44–47. |
| No. 1.089 | Bowman, J. D., Silva, N., Schüftan, E., Almeida, J. M., Brattig-Correia, R., Oliveira, R. A., Tüttelmann, F., Enard, D., Navarro-Costa, P., & Lynch, V. J. (2024). Pervasive relaxed selection on spermatogenesis genes coincident with the evolution of polygyny in gorillas. eLife, 13, RP94563. |
| No. 1.090 | Keeffe, R. M., & Brennan, P. L. R. (2023). Vaginas. Current Biology, 33(12), R670–R674. |
| No. 1.091 | Natural History Museum. (2019, January 30). What is more impressive than a walrus’s tusks? [Video]. YouTube. |
| No. 1.092 | Laidre, M. E. (2019). Private parts for private property: Evolution of penis size with more valuable, easily stolen shells. Royal Society Open Science, 6(1), 181760. |
| No. 1.093 | Roselli, C. E., & Stormshak, F. (2009). Prenatal programming of sexual partner preference: the ram model. Journal of neuroendocrinology, 21(4), 359–364. |
| No. 1.094 | Shadle, A. R. (1946). Copulation in the porcupine. The Journal of Wildlife Management, 10(2), 159–162. |
| No. 1.095 | Kākā cloaca, Judi Lapsley Miller, Wikimedia Commons, CC BY 4.0 |
| No. 1.096 | Velando, A., Eiroa, J., & Domínguez, J. (2008). Brainless but not clueless: earthworms boost their ejaculates when they detect fecund non-virgin partners. Proceedings. Biological sciences, 275(1638), 1067–1072. |
| No. 1.097 | Bourke, D. (1998). An introduction to the unique reproductive physiology and breeding activity of SACs. In Proceedings of the International Alpaca Conference (Fremantle, WA). |
| No. 1.098 | Orbach, D. N., Kelly, D. A., Solano, M., & Brennan, P. L. R. (2017). Genital interactions during simulated copulation among marine mammals. Proceedings of the Royal Society B, 284(1864), 20171265. |
| No. 1.099 | Funnell, R. (2023, October 10). How do sloths have sex? It begins with a female screaming in D sharp. IFLScience. |
| No. 1.100 | Michiels, N., & Newman, L. (1998). Sex and violence in hermaphrodites. Nature, 391, 647. |
| No. 1.101 | Wulff, N. C., van de Kamp, T., Dos Santos Rolo, T., Baumbach, T., & Lehmann, G. U. (2017). Copulatory courtship by internal genitalia in bushcrickets. Scientific reports, 7, 42345. |
| No. 1.102 | Johnston, S. D., Smith, B., Pyne, M., Stenzel, D., & Holt, W. V. (2007). One‐sided ejaculation of echidna sperm bundles. The American Naturalist, 170(6), E162–E164 |
| No. 1.103 | Hedrick, B.P., Antalek-Schrag, P., Conith, A.J., Natanson, L.J. and Brennan, P.L.R. (2019), Variability and asymmetry in the shape of the spiny dogfish vagina revealed by 2D and 3D geometric morphometrics. J Zool, 308: 16-27. |
| No. 1.104 | C. Meslin, T.S. Cherwin, M.S. Plakke, J. Hill, B.S. Small, B.J. Goetz, C.W. Wheat, N.I. Morehouse, & N.L. Clark. (2017). Structural complexity and molecular heterogeneity of a butterfly ejaculate reflect a complex history of selection, Proc. Natl. Acad. Sci. U.S.A. 114 (27) E5406-E5413. |
| No. 1.106 | Koene, J. M. (2006). Tales of two snails: Sexual selection and sexual conflict in Lymnaea stagnalis and Helix aspersa. Integrative and Comparative Biology, 46(4), 419–429. |
| No. 1.107 | Herrera, A. M., et al. (2013). Developmental basis of phallus reduction during bird evolution. Current Biology, 23(12), 1065–1074. |
| No. 1.108 | Neufeld, C. J., & Palmer, A. R. (2008). Precisely proportioned: intertidal barnacles alter penis form to suit coastal wave action. Proceedings. Biological sciences, 275(1638), 1081–1087. |
| No. 1.109 | Yllera, M. D. M., Alonso-Peñarando, D., & Lombardero, M. (2023). Gross Anatomy of the Female Reproductive System of Sugar Gliders (Petaurus breviceps). Animals : an open access journal from MDPI, 13(14), 2377. |
| No. 1.110 | Family of lions during mating season, Byrdyak, Wikimedia Commons, CC BY-SA 4.0 |
| No. 1.111 | Crews, D., Grassman, M., & Lindzey, J. (1986). Behavioral facilitation of reproduction in sexual and unisexual whiptail lizards (Reptilia: Teiidae). Proceedings of the National Academy of Sciences of the United States of America, 83, 9547–9550. |
| No. 1.112 | Glaeser, S. S., Edwards, K. L., Paris, S., Scarlata, C., Lee, B., Wielebnowski, N., Finnell, S., Somgird, C., & Brown, J. L. (2022). Characterization of Longitudinal Testosterone, Cortisol, and Musth in Male Asian Elephants (Elephas maximus), Effects of Aging, and Adrenal Responses to Social Changes and Health Events. Animals : an open access journal from MDPI, 12(10), 1332. |
| No. 1.113 | Sivinski, J. (1978). Intrasexual aggression in the stick insects Diapheromera veliei and D. covilleae and sexual dimorphism in the Phasmatodea. Psyche, 85. |
| No. 1.114 | Ramm, S. A., Schlatter, A., Poirier, M., & Schärer, L. (2015). Hypodermic self-insemination as a reproductive assurance strategy. Proceedings of the Royal Society, 282(1811), 20150660. |
| No. 1.115 | Watts D. P. (2007). Effects of male group size, parity, and cycle stage on female chimpanzee copulation rates at Ngogo, Kibale National Park, Uganda. Primates; journal of primatology, 48(3), 222–231. |
| No. 1.116 | University of California Museum of Paleontology. (n.d.). Porifera (sponges). UCMP. |
| No. 1.117 | Pullen, S. L., Bearder, S. K., & Dixson, A. F. (2000). Preliminary observations on sexual behavior and the mating system in free-ranging lesser galagos. (Galago moholi). American journal of primatology, 51(1), 79–88. |
| No. 1.118 | Brennan, P. L. R., Clark, C. J., & Prum, R. O. (2010). Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia. Proceedings of the Royal Society B, 277(1686), 1309–1314. |
| No. 1.119 | Common lizard with everted hemipenes, Timothy A. Gonsalves, Wikimedia Commons, CC BY-SA 4.0 |
| No. 1.120 | Tūhura Otago Museum. (2019, September 5). Roo Balls! Otago Museum Blog. |
| No. 1.121 | Douglas, P. H., Hohmann, G., Murtagh, R., Thiessen-Bock, R., & Deschner, T. (2016). Mixed messages: wild female bonobos show high variability in the timing of ovulation in relation to sexual swelling patterns. BMC evolutionary biology, 16(1), 140. |
| No. 1.123 | Tina Shaw. (2020, February 23). Eagle trio sees parenting success in Illinois. U.S. Fish & Wildlife Service. |
| No. 1.124 | Chase, R. (2007). Gastropod reproductive behavior. Scholarpedia, 2(9), 4125. |
| No. 1.125 | Waterman J. M. (2010). The adaptive function of masturbation in a promiscuous African ground squirrel. PloS one, 5(9), e13060. |
| No. 1.126 | Stockley, P., Franco, C., Claydon, A. J., Davidson, A., Hammond, D. E., Brownridge, P. J., Hurst, J. L., & Beynon, R. J. (2020). Revealing mechanisms of mating plug function under sexual selection. Proceedings of the National Academy of Sciences of the United States of America, 117(44), 27465–27473. |
| No. 1.127 | Hippo rear, Kafue, Zambia, Timothy A. Gonsalves, Wikimedia Commons, CC BY-SA 4.0 |
| No. 1.128 | Yoshizawa, K., Ferreira, R. L., Kamimura, Y., & Lienhard, C. (2014). Female penis, male vagina, and their correlated evolution in a cave insect. Current Biology, 24(9), 1006–1010. |
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