The database was constructed through a systematized search of peer-reviewed papers on Web of Science (WoS) regarding the reproductive behavior of Neotropical dung beetles. The search was conducted in the second semester of 2022, covering articles published between 1980 and 2022. We employed the following search terms across the title, abstract, and keywords of each paper: [“dung beetle*” OR Scarabaeinae OR Aphodiinae OR Geotrupidae) AND (“reproductive behavior*” OR reproduct* OR etholog* OR behavior* OR “reproductive success” OR mating* OR “mating success” OR competition OR combat OR contest) AND (nest* OR nesting OR “nesting behavior” OR “resource reloca*” OR “food reloca*” OR “resource reloca*” behavior OR “resource reloca* behavior”].

Studies on various aspects of the reproductive behavior of the Scarabaeidae (Aphodiinae and Scarabaeinae) and Geotrupidae were conducted in 15 countries, ranging from Mexico to Argentina (Figure 4). The recorded species were found mainly in three countries: Mexico (38%), Argentina (28%), and Brazil (21%). The remaining countries had less than three species analyzed (Table 1).

The diversity of localities followed the same order mentioned by country. In Mexico, most of the localities referred to in the studies correspond to 16 states, mainly Veracruz, Chiapas, and the State of Mexico. In Argentina, we recorded 11 provinces, including La Rioja, Jujuy, and San Luis. Brazil included seven states, of which São Paulo and Minas Gerais were most frequently mentioned. Colombia and Uruguay had five and four departments, respectively. For each of the remaining countries, only one or two localities are cited (Figure 4).

Considering the family or subfamily of the beetles evaluated, Scarabaeinae was the most studied group in almost all countries, followed by Aphodiinae, studied only in Mexico and Uruguay, and Geotrupidae, studied only in Mexico and Chile. At the level of the Scarabaeinae tribes, Deltochilini was studied in nine countries, followed by Phanaeini in eight countries, and Dichotomiini, Oniticellini, and Onthophagini in six countries. The Eucraniini tribe was studied exclusively in Argentina, and Coprini in Mexico (Table 1).

Among the Scarabaeinae genera, Canthon Hoffmannseg was the most represented, with 22 species in five countries, followed by Onthophagus Latreille with 13 species distributed in six countries, Eurysternus Dalman with 10 species in six countries, Deltochilum Eschscholtz with nine species in five countries, and Dichotomius Hope with nine species in four countries (Table 2).

The habitats where dung beetles display their feeding or reproductive behaviors were mentioned for approximately 97% of the recorded species (Table 2). About half of these species live in native or introduced open environments, such as grasslands in tropical and temperate zones of Mexico, the Pampean region and grasslands of Uruguay, the steppes of Argentina, and the savanna of Brazil. In multiple studies (64%), specimens were collected in fields or pastures dedicated to livestock raising. The species studied within grassland ecosystems were mainly burrower Scarabaeinae (36), with type I, II, or III nesting patterns. Studies on the behavior of roller and non-nesting Aphodiinae species in grasslands were lower (11 and 9, respectively; Table 2; Supplementary Table S3).

Behavioral studies on species collected in forest environments represent one-third of the total; these forest ecosystems include tropical rain forests, temperate mountain forests, or xeric forests, and fruit or forest plantations. Among the species of Scarabaeinae studied in forest ecosystems, 28 were burrower species, and 24 were roller species. A small proportion of all studied species (less than 10%) were recorded in a variety of habitats including native forests, grassland environments, and silvopastoral systems (i.e., Canthon virens (Mannerheim) and Diabroctis cadmus Harold (Forti et al., 2012; Halffter et al., 2013; Murillo-Ramos et al., 2016). Similarly, Canthon cyanellus cyanellus LeConte (Martínez, 1992a,b), and C. imitator Brown (Martínez et al., 2019) were collected in both tropical forests and neighboring pastures or crops. The burrower species Onthophagus curvicornis Latreille (Montes-Rodríguez, 2017), Ceratotrupes fronticornis (Erichson; Ramírez-Restrepo and Halffter, 2016), and Dichotomius satanas (Harold; Barretto et al., 2021a,b), which generally occurs in forest environments, also display their activities in pastures dedicated to livestock raising, crops, and even in urban or semi-urban areas. Finally, the tribe Eucraniini represented about 10% of the recorded species studied. These are exclusive burrowers of arid and semi-arid environments, endemic to the northwestern region of Argentina (Zunino et al., 1989; Monteresino and Zunino, 2003; Ocampo, 2005, 2010; Ocampo and Philips, 2005).

Coprophagous burrower beetles may feed directly on food or build subterranean galleries to store and later consume the resource during the pre-reproductive stage (Halffter and Matthews, 1966; Halffter and Edmonds, 1982; Halffter et al., 1985; Hanski and Cambefort, 1991; Ocampo and Hawks, 2006; Scholtz, 2009). The pre-reproductive behavior has been studied in detail in eight species of Phanaeus (Halffter et al., 1974; Halffter and López, 1977; Price and May, 2009; Huerta et al., 2010). These Phanaeus species roll pieces of food some distance away from the source, pushing them with the head and forelegs (butting behavior), then burying them in a feeding gallery for subsequent consumption. According to Huerta and Halffter (2000), in three species of Copris Müller (C. armatus Harold, C. lugubris Boheman and C. incertus Say) during the feeding stage, males preferentially store food in sausage-shaped galleries, while females accumulate food masses or nest cakes in subterranean chambers, rather than galleries.

Coprophagous and necrophagous roller species cut and transport a food ball at different distances from the food source, which is used for feeding by sexually immature beetles or nesting by sexually mature beetles (Matthews, 1963; Halffter and Matthews, 1966; Halffter and Edmonds, 1982). During rolling, the beetle pushes the ball with the hind and middle legs; the forelegs are applied on the ground to move the ball. This rolling position is known as the pushing position (Halffter and Matthews, 1966). Most Neotropical species move food by the pushing position. During rolling, the food ball is covered by a layer of soil to avoid its drying out and the arrival of other competitors; in addition, the food ball is protected by chemicals from the exocrine glands of the abdominal and pygidia region of the beetles (Bellés and Favila, 1983; Pluot-Sigwalt, 1988a,b, 1991). The substances released by these glands play multiple functions: defense against competitors such as flies; fungicides or fungistatic; pheromones, and prevention of food decomposition, allowing its consumption by larvae in the brood ball (Favila et al., 2012). However, various species of the genus Canthon (e.g., C. septemmaculatus, Latterille, C. tristis, Harold, C. obliquus Horn, C. edentulus Harold) and Deltochilum orbignyi Blanchard form the food ball but do not roll it; instead, they bury it shallowly below the food source (Halffter and Matthews, 1966; Halffter and Halffter, 1989; Halffter et al., 2013). Eurysternus species are considered roller beetles; however, they feed and nest directly below the food source during the pre-reproductive and reproductive stages, respectively (Huerta et al., 2003).

Studies on male competition for food or potential nesting partners are scarce in Neotropical coprophagous dung beetles. Studies on fights between females for food resources are even scarcer. Fight dynamics during the pre-reproductive and reproductive stages have been mentioned or addressed in field and laboratory studies of only six species: Phanaeus tridens, Laporte, Onthophagus acuminatus, Harold, Canthon quinquemaculatus, Laporte, C. lituratus, Germar, C. bispinus Germar, and C. cyanellus (Halffter and Edmonds, 1982; Favila, 1988; Favila and Díaz, 1996; Rodrigues and Flechtmann, 1997; Price and May, 2009; Halffter et al., 2013; Cantil et al., 2014b; González-Vainer, 2015; Salomão et al., 2019).

Pre-reproductive field records on the combat behavior between Phanaeus tridens males showed that the winner joins a female, pushing and burying the excrement fragment next to her. Male fights associated with food thievery, gallery invasion and fights between females have been documented in this species (Halffter and Edmonds, 1982; Price and May, 2009). Different fighting strategies for the gallery and the female have been observed in Onthophagus acuminatus, where the male owner guards the gallery entrance against intruders and periodically patrols along the tunnel (Emlen, 1997). The owner male fighting to defend the tunnels is horned and mates repeatedly with the occupant female. Intruder males can confront the owner and fight until one of them leaves the tunnel. However, hornless intruder males can also sneak inside, avoiding the guarding male. The intruder male digs side tunnels that intersect guarded tunnels and stealthily copulates with the female of the nest-owning male (Emlen, 1997). The guarding male can catch sneaking males before encountering the female. In this case, sneaking males return to their side tunnels or build new tunnels and remain inactive for several hours, but later they attempt to enter the primary tunnel again in search of the female (Emlen, 1997).

Regarding Canthon quinquemaculatus and C. lituratus, the theft or splitting of the food ball during rolling has been frequently observed. Specifically, in C. quinquemaculatus a case is mentioned where the male rolling the food ball with a female was displaced by the intruder and the female that was rolling with the owner male remained with the thief (Rodrigues and Flechtmann, 1997; Halffter et al., 2013; Cantil et al., 2014b). In C. bispinus, intrasexual fights for the food ball were recorded during the food ball rolling and burying by male–female pairs (González-Vainer, 2015).

Fights in Canthon cyanellus have been extensively documented in field and laboratory studies. Fights occur mainly between males during the breeding season; intruder males attempt to steal the food ball and the female is transported by an owner male to the nesting site (Favila and Díaz, 1996; Chamorro-Florescano and Favila, 2008). Differences in body size and the reproductive status of females and males (virgins or with previous nesting) influence the fighting success between contestant males for the females transported in the food ball (Chamorro-Florescano and Favila, 2008; Chamorro-Florescano et al., 2011). In Copris laeviceps Harold, fights during nesting have also been documented but generated by experimentally placing an intruder female in a nest where brood balls are looked after by a resident female (Klemperer, 1986). Klemperer (1986) also reported cases of a female taking care of brood balls constructed by another female in a foreigner nest.

Copulation is not easy to observe because it mainly occurs in underground galleries, making it difficult to determine when and how it happens. However, we found information on different aspects of the copulation behavior in 73 species of Neotropical Scarabaeinae beetles (Table 3). The copulation process has been described for only seven species: Megathoposoma candezei (Harold; Wille, 1973), Phanaeus daphnis, P. mexicanus (Halffter and López, 1977), Liatongus rhinocerulus (Bates; Halffter and Edmonds, 1982), Canthon cyanellus, C. indigaceus chevrolati (Martínez and Cruz, 1990), and Onthophagus acuminatus (Emlen, 1997).

Halffter and López (1977) defined four stages during copulation: (a) approach of the male to the female, generally near the food source as a meeting place; (b) detection of the female by the male; (c) positive response of the female and male mounting on her and attaching his parameres at the genital opening; (d) insertion of the male aedeagus. During this last stage, males can remain still or include touching or tapping movements with their front legs on the thorax, elytra, or sides of the female, supposedly intended to keep it calm. Although Halffter and Edmonds (1982) considered that there is no elaborate pre-copulatory or courtship behavior among Scarabaeinae, Emlen (1997) interpreted the tapping behavior observed in several species of insects as a copulatory courtship. Finally, at the end of copulation, the male separates and may remain near the female, guarding it against other males, or he may bury himself, searching for food or leaving the nest, depending on the species.

Details related to the site, time, or duration of copulation are only known for 34 species (Table 3), 14 of which are Canthon species because these are more easily observed during the rolling of food balls, and for seven Eurysternus species next to the food source. The remaining copulation observations correspond to species for which male–female pairs were found at their gallery entrance. A first copulation during the pre-nesting stage, which allows females to complete oocyte maturing and initiate the nesting stage, has only been observed in Phanaeus mexicanus, P. daphnis, Canthon cyanellus cyanellus, C. indigaceus chevrolati, Copris incertus, and Eurysternus mexicanus Harold (Halffter et al., 1976; Halffter and López, 1977; Martínez and Cruz, 1990; Martínez et al., 1996; Huerta et al., 2003). Most copulations observed on the surface at the gallery entrance occur before the nest ball or mass elaboration stage. The copulation duration varied from very short, lasting only one or 2 min in Coprophanaeus ensifer (Germar) and Onthophagus acuminatus (Emlen, 1997; Lira and Frizzas, 2022), up to maximum times of 75 min in Canthon cyanellus cynellus (Martínez and Cruz, 1990) and 84 min in Eurysternus caribaeus (Herbst; Huerta et al., 2003). The remaining observed cases ranged from 5 to 40 min (Table 3).

Sperm competition in Neotropical dung beetle species has only been studied in Canthon cyanellus, observing that the male repeatedly copulates during nesting and before and during the elaboration of nest balls (Favila et al., 2005). It was experimentally demonstrated, with a cuticular genetic marker, that with this behavior, males significantly increase their paternity under a sperm competition scenario (Favila et al., 2005). In another study, Chamorro-Florescano and Favila (2009) found that males regulate copulation frequency during nesting; if the female has already copulated with other males, the latest male increases copulation frequency between the elaboration of nest balls; however, when a male is nesting with a virgin female, he does not mate several times. Besides, only males with previous reproductive experience increase their paternity, contrary to virgin males; that is, the reproductive experience of the female affects the frequency of mating, and the reproductive status of the male affects its reproductive success during the nesting stage (Chamorro-Florescano and Favila, 2009). In Canthon edentulus, copulations have also been observed during the nest care period (Halffter et al., 2013), suggesting that in this species, sperm competition also occurs and that the male can reduce it by repeated mating.

Cryptic choice by females can lead to direct or indirect benefits when choosing the male with whom they will mate (Andersson, 1994). The behaviors of males during combats may be signals allowing females to evaluate and select the most successful males; this, in turn, may be related to attributes indicative of male “quality” (Berglund et al., 1996; Briffa and Sneddon, 2007). Few studies of Neotropical beetles have recorded female behaviors that may reflect the choice or preference towards males with particular attributes. For example, Canthon cyanellus females that rolled together with a male were observed to actively participate during male–male combat over attempted ball-stealing by an intruder male, favoring and selecting males with reproductive experience, i.e., with previous mating and nesting (whether intruder or owner) over virgin males (Chamorro-Florescano et al., 2011). Another study found that the combat outcome can significantly affect the reproductive success of both combatants. Winning males increase their acquired paternity under conditions of sperm competition compared to loser males in previous combats (Chamorro-Florescano and Favila, 2016; Chamorro-Florescano et al., 2017).

Sperm competition and cryptic female choices play an essential role for dung beetles during and after copulation. Females copulating with different males may store sperm indefinitely until oocyte fertilization (Halffter and Edmonds, 1982; Eberhard, 1996). However, multiple factors can affect these dynamics. Sexual recognition in dung beetles occurs through cuticular hydrocarbons (Ortiz-Domínguez et al., 2006). These compounds act as short-distance contact pheromones and vary according to several factors, such as the changes at the gonad level in females and males during reproduction (Halffter and López, 1977; Huerta et al., 1981; Martínez and Cruz, 1990; Martínez, 1992b; Martínez and Huerta, 1997; López-Guerrero and Halffter, 2000; Howard and Blomquist, 2005; Huerta and Martínez, 2008; Ginzel, 2010; Favila et al., 2012).

The spermatheca plays a fundamental role in sperm competition and the cryptic choices of females. In Scarabeinae and Aphodiinae, the spermatheca is characterized by a C-shaped sclerotized receptacle with a striated muscle that joins the distal and basal end and a duct. After copulation, sperm migrates through this duct from the spermatophore or seminal fluid to the receptacle, where it is maintained and released until oocyte fertilization (López-Guerrero and Halffter, 2000; Martínez et al., 2001). In the family Geotrupidae, tribe Geotrupini, the spermatheca is pyriform with transverse striations at the base. In most species, it is elongated and has a short duct. Studies suggest that this type of spermatheca is primitive compared to those found in Scarabaeinae (Halffter and Edmonds, 1982; Martínez and Trotta-Moreu, 2010). Although both females and males obtain various benefits by mating with different partners, sperm competition may continue even after copulation under this scenario. However, the female may also perform sperm choice of specific phenotypes by shedding sperm and biasing sperm utilization by muscle contractions, among other possible mechanisms (Eberhard, 1996). These mechanisms have not been explored, but it has been reported that C. cyanellus females may benefit certain males having reproductive experience and a successful combat outcome (Chamorro-Florescano and Favila, 2016; Chamorro-Florescano et al., 2017).

Chemical communication occurs through semiochemicals, either pheromone for intraspecific interactions or allelochemicals for interspecific interactions (Cortez, 2013). In dung beetles, both compounds are produced by exocrine glands distributed throughout the body, varying according to species and sex, as seen in Canthon cyanellus, C. indigaceus chevrolati and C. femoralis Chevrolat (Favila, 1988, 2001; Pluot-Sigwalt, 1988a,b). However, other attributes influence differences at the glandular level; for example, roller beetles have more exocrine glands than burrower beetles (Pluot-Sigwalt, 1991; Halffter et al., 2013). Glandular asymmetry has evolved in response to the different ecological pressures experienced by roller and burrower beetles, such as the relocation of the food resource competed by conspecific and heterospecific individuals (Hanski and Cambefort, 1991; Favila, 2001).

Since sexually active beetles can also find each other around food to form reproductive pairs, the presence of short- and long-distance sex pheromones during this stage has been suggested (Favila et al., 2012, 2016; Halffter et al., 2013). Recognition in sexually active males and females occurs when both individuals meet, extend their antennae, and touch each other. With this behavior, they can recognize each other through short-distance cuticular compounds. Immature and same-sex individuals will not display cooperative behavior. However, individuals of different sexes or sexually mature collaborate in elaborating and rolling the food ball for subsequent nesting, as demonstrated in C. cyanellus (Ortiz-Domínguez et al., 2006).

Long-distance pheromone emission by males has been described in different species of dung beetles, attributed as a strategy to attract females for nesting. However, it has also been suggested that the compounds emitted may repel other males or act as defensive chemicals against potential predators (Favila et al., 2016). During pheromone emission, the male holds the first and second pairs of legs upside down and rubs the abdominal sternites with the hind legs, where several exocrine glands are located. At synchronized time intervals, it rubs its legs and lifts them into the air (Tribe, 1975; Favila and Díaz, 1996; Favila, 2001). This behavior has been reported in different species of dung beetles next to the food source or a food ball, irrespective of whether a female is present, such as Canthon bispinus, C. chalybaeus, Blanchard, C. femoralis, C. cyanellus, C. lituratus, C. virens. However, in all these species, no female was observed arriving (Bellés and Favila, 1983; Favila and Díaz, 1996; Rodrigues and Flechtmann, 1997; Silveira et al., 2006; Vaz-de-Mello and Génier, 2009; Favila et al., 2012; Halffter et al., 2013; Cantil et al., 2014b; González-Vainer, 2015; Martín et al., 2021). In C. cyanellus and C. quiquemaculatus, the male exhibits this behavior in a nest where a female is already present (Bellés and Favila, 1983; Cantil et al., 2014b). However, two unidentified male species of Dendropaemon Perty were observed releasing pheromones, displaying the same behavior described at the chamber entrance. The arrival of a female touching the male’s abdomen during the emission behavior, has been described as a recognition behavior in the nesting site, and after this sexual recognition, they enter the gallery (Vaz-de-Mello and Génier, 2009). In C. femoralis, once the male buries the food ball, he performs the pheromone emission behavior until the arrival of the female (Favila, 2012).

Allomones are another multifunctional chemical found in dung beetles, related to defense, aggression, and protection of the food resource and the nest. This behavior has been explored in C. cyanellus, C. femoralis and Deltochilum furcatum Laporte (Halffter and Edmonds, 1982; Bellés and Favila, 1983; Favila, 2001; Cortez et al., 2012, 2015; Favila et al., 2012; Ix-Balam et al., 2018). An example of the above is the secretion of the pygidial glands of C. cyanellus, which produce chemicals that act as a defensive substance against Camponotus sericeiventris Guérin-Méneville (Cortez et al., 2012). When the ant attempts to attack C. cyanellus, it approaches the beetle and touches its body with its antennae. However, defensive compounds repel it, such as phenol in C. cyanellus and geraniol secreted by the pygidial glands of C. femoralis, or guaiacol produced by the pygidial glands of C. cyanellus (Favila, 2001; Cortez et al., 2012). In both species, the importance of the compounds released to impregnate and protect the brood balls from fungi has been proven. Canthon cyanellus displays nest care during almost all larval development and until the emergence of teneral adults, while C. femoralis does not look after the brood ball constructed by the female (Bellés and Favila, 1983; Favila, 2001; Favila et al., 2012). Deltochilum furcatum is another species that does not show nest care. It is suggested that pygidial secretions can reduce the oviposition of Lucilia cuprina Wiedemann flies on food balls rolled by beetles. However, whether this is due to the effect of secretions on microbial activity or an allomone effect is unknown (Ix-Balam et al., 2018).

The pygidial and abdominal secretions with which dung roller beetles impregnate nest balls during rolling are not only essential to avoid heterospecific competition. The chemicals secreted by the pygidial glands of C. cyanellus and C. femoralis, such as acetic acid and benzoic acid, have been found to prevent the decomposition of the food with which beetles elaborate nest balls and on which larvae feed until emergence. These compounds also have microbial activities (Favila, 1993; Cortez et al., 2012; Favila et al., 2016).

Subsocial behavior involving nest care by the female until the emergence of offspring is considered a relatively rare behavior within the Scarabaeinae (Halffter et al., 2013). Only 18 species of three genera have been identified in the Neotropical zone, mainly Copris and some Canthon and Eurysternus species, which take care of the nest until a particular stage of preimaginal development. Of special note is the contribution of males during the nest-care phase, albeit for a short time, in five Canthon species (Halffter et al., 2013; González-Vainer, 2015) (Table 4).

The nest care duration varies among species, particularly those that have annual cycles and live in temperate zones, such as Copris armatus and C. sierrensis Matthews, which look after the nest for more than seven and eight months, respectively, until the emergence of the imago, after the winter season ends and temperature improves (Anduaga et al., 1987; Huerta et al., 2010). The other Copris species studied are found in more tropical areas, allowing them to have shorter cycles. In these species, care time varies from 47 days on average in C. laeviceps to 78 and 88 days on average in C. lugubris and C. incertus, respectively (Anduaga et al., 1987; Martínez et al., 1996). Four Canthon species, Malagoniella bicolor (Guerin) and Megathopa violacea Blanchard have been identified among the roller dung beetles that perform nest care almost until imago emergence. Canthon rutilans cyanescens Harold and Malagoniella punticollis (Blanchard) only care for the nest until the larval stage. Canthon virens is a particular case, as several studies report that these perform nest-care only during the larval stage, requiring further confirmatory research (Forti et al., 2012; Halffter et al., 2013). In Canthon mutabilis Harold, females and males look after the nest only for eight and 5 days, respectively, of the 23 days of preimaginal development (Halffter et al., 2013; Table 4). In Canthon cyanellus, the female cares for the nest until the hatching of the offspring, while the male stays in the nest until the female constructs all the brood balls, taking care of both the brood balls and the female to avoid other males mating her (Favila, 1993; Favila et al., 2005).

Among the 11 species of Eurysternus studied, seven take care of the nest; in two species, it is undefined whether or not they perform nest caring, and only E. jessopi Martínez has been described as not taking care of the nest. The known duration of preimaginal development in this genus varies from 21 days in E. inflexus Germar to 83 days on average in E. marmoreus Laporte (Huerta et al., 2003, Table 4).

Of all the Neotropical Scarabaeinae species studied, the duration of preimaginal development until the emergence of the imago is known for 43 species. Many species complete their development until emergence within one to two months, as observed in some members of the tribes Deltochilini, Onthophagini, Coprini, Oniticellini, and Dichotomini (Table 4). Dichotomius (L.) carbonarius (Mannerheim) and Attavicinus monstrosus (Bates) are the only species for which the duration of the larval stage is known. In Copris sierrensis, Dichotomius colonicus (Say), and Phanaeus quadridens (Say), under field conditions, there were still pupae and imagos without emerging 8 months after the onset of preimaginal development, perhaps because they inhabit a temperate zone and were awaiting a more favorable climate to surface (Huerta et al., 2010; Table 4). Therefore, further field or laboratory studies are needed to broaden our understanding of the preimaginal development of multiple dung beetle species, of which little or nothing is currently known.

The fecundity — the number of eggs a female lays over its lifetime — can be considered high in the Aphodiinae (Halffter and Edmonds, 1982). Their nesting behavior is quite simple. The Geotrupidae show a moderate fecundity, with some effort invested in nest building. Finally, in Scarabaeinae, fecundity is relatively low but is compensated by greater reproductive effort or nesting complexity, which may include nest care (Table 5). In this case, some Copris species elaborate one to five nests per year or breeding season, with an average of three or four balls per nest (Anduaga et al., 1987; Martínez et al., 1996; Huerta et al., 2010). Also, Eurysternus species show a low fecundity, with two to three nests per season and three to five balls per nest, but their nesting behavior can be highly complex. For example, E. balachowskyi Halffter and Halffter, E. caribaeus, E. marmoreus, and E. mexicanus build temporary nests that are destroyed before the final nest, implying the likely loss of offspring and a higher fecundity (Huerta et al., 2003). The species with a simpler behavior and low fecundity include Liatongus rhinocerulus Bates, which makes only a single nest per season, consisting of a branched gallery with 6 or 7 nest masses (Anduaga and Halffter, 1993).

Halffter and Edmonds (1982) considered that most Scarabaeinae species produce an average of 20 eggs per female over their lifetime, which still requires significant field and laboratory work to confirm. Although there is plenty of data regarding the nesting behavior of Neotropical species, only 18 species have information on the number of nests or brood balls, brood masses per nest, or galleries built by females over their lifetime or per breeding season. Moreover, 41 species have only partial information. Therefore, there are few species for which the relative fecundity per breeding season is known, obtained from the average number of balls or brood masses produced in each nest. The species known to produce an average of more than 20 eggs over their lifetime or per breeding season include four roller dung beetles: Canthon mutabilis (22.5), C. cyanellus (37.5), C. indigaceus chevrolati (42), and C. edentulus (50). On the other hand, those elaborating less than 10 balls or brood masses per breeding season are four species of Eurysternus, two of Copris, two of Onthophagus, and two of Canthon (Table 5). In most cases, only the number or type of nest balls or masses found in the field are reported, but further data are required to estimate their fecundity by season.

Studies on the reproductive behavior of the subfamily Aphodiinae are few, consisting of scarce data on eight species of Aphodiini and three of Eupariini, mainly from Mexico. They are coprophagous dwellers that do not build nests but lay their eggs in the dung or at the dung-soil interface, depending on the species (Figure 6). The knowledge state of gonad maturity in both sexes helped to distinguish young from already mature individuals, as in Gonaphodiellus opisthius (Bates), Cephalocyclus hogei, (Bates) Planolinellus vittatus (Say), and the three Ataenius Harold species studied (Cruz et al., 2002; Martínez and Suárez, 2012; González-Vainer et al., 2018). The other species practically emerge mature and ready to reproduce. Most of the lifetime of Aphodiinae beetles is spent in the preimaginal stages or diapause; when adults emerge, they have a short period of activity lasting two or 3 months to reproduce, and then they die (Table 6).

Although there are data available on the phenology and reproductive cycles of several species of Mexican Aphodiini (see Martínez et al., 2022), information on their reproductive behavior is scarce, including mating and oviposition, since they are not easy to observe given their small size and because they spend most of their time inside the dung pats. Martínez et al. (2022) synthesize the available information on the reproductive cycles of some Aphodiini: Agrilinellus ornatus (Schmidt), G. opisthius, and Liothorax levatus (Schmidt), by characterizing mature, maturing, or immature individuals by ovary size variations, and the presence or absence of spermatozoa in the female spermatheca once they have already copulated. While in males, it is mainly due to the size of the glandular reservoir. In Eupariini, besides the anatomical variations mentioned to characterize the maturity state of individuals, in Ataenius perforatus Harold was possibly observed copulating inside the dung mass, at the end of which a spermatophore is formed in the vagina of females. This structure was also observed in the other two Ataenius species studied and only in a single Aphodiini species (Cephalocyclus hogei; Cruz et al., 2002). The number of eggs laid is known for some species, such as G. opisthius, which lays 15 to 18 agglutinated eggs in an underground chamber under the manure, and Blackburneus saylorea (Robinson), which lays eight eggs per nesting chamber in the two to three chambers it builds over its lifetime (Cruz et al., 2002). In Planolinellus vittatus, each egg is deposited in a laying chamber built within the manure still wet from the manure crust, although the total number of eggs laid per female is not reported (Martínez, 2008). On the other hand, in the three studied Ataenius species, eggs may be laid either under the manure or at the manure-soil interface; the number of eggs laid varies from 10 to 18 eggs per clutch. Finally, the time elapsed from preimaginal development to imago formation is known for only three Aphodiini species and all three Eupariini species. This time varies from 19 days to 66 days. The development time of each preimaginal stage is known for only four species; most of this time is spent in the larval stage (Table 6).

Studies on the reproductive behavior of Geotrupidae species are also scarce in the Neotropics. There are data on only four species belonging to two tribes — Ceratotrupini and Geotrupini —of which three are Mexican, and one is Chilean (Supplementary Table S4). All these species are coprophagous and paracoprid; the exception is Taurocerastes patagonicus, considered roller or telecoprid for moving food with its front legs; it is also a rare species that does not fly (Howden and Peck, 1987).

The species with the best-known reproductive behavior is Geotrupes cavicollis, observed under laboratory conditions (Halffter et al., 1980b, 1985); there is less information for the other species (Supplementary Table S4). This species also undergo maturation after emerging, and immature individuals build simple feeding galleries near or under the manure at a maximum depth of 10 cm. This period lasts 35 to 40 days after emergence; the reproductive period begins when the male and the female copulate at the gallery entrance for 10 min. Food is stored in galleries with the couple’s collaboration during this period. The nest comprises a maximum of five galleries, each with one egg in the distal end. In rare cases, two eggs can be laid per gallery, with soil in between the two eggs; the second was laid 24 h after the first. The subsequent oviposition took place 10 to 15 days later. Geotrupidae nest range between eight to 21 cm in depth, depending on the galleries and their radial or parallel distribution, with an average length of 21.5 cm. According to Halffter et al. (1980b, 1985), for the female to continue laying more than one or two eggs, the male must copulate and help with nest provisioning. Within each brood mass, preimaginal development starts with the embryo, and it takes 10 days for the larva to hatch; the larval stage lasts 210 days, followed by pupae, which take 44 days, and then the adult or imago remains in the nest for 30 to 40 days before emerging to the surface. Females die after 80 to 90 days (maximum 140 days) and only lay five eggs over their lifetime. However, females of G. cavicollis still have large oocytes not laid, differing from Scarabaeinae and Aphodiinae species, in which females show the reduction of their oocytes before dying (Martínez, 1992a,b; Martínez et al., 1996; Martínez, 2008; Martínez and Suárez, 2012).

Regarding the other species, Ceratotrupes fronticornis (Erichson) buries dog feces to build nests, but the type of the nest is not mentioned (Ramírez-Restrepo and Halffter, 2016). In Geotrupes (Halffterius) rufoclavatus Jekel, females oviposit in February because they have matured or maturing ovaries; however, no information is available on their oviposition behavior or the type of nest (Trotta-Moreu et al., 2007). Finally, in Taurocerastes patagonicus, one study describes that food is moved as pellets, then buried in simple, winding galleries inclined 70° and measuring 10 to 35 cm long (Howden and Peck, 1987). At the bottom, they accumulate food, forming a mass 5 to 7 cm long by 2 to 3 cm high. Nevertheless, it is not mentioned whether this food is only for adults or also for the young. Although male–female pairs were observed inside the gallery with food, no eggs were found. In another site, larvae were observed buried at 35 cm depth, although not associated with any food reserve or mass (Howden and Peck, 1987). Further studies are required to clarify this peculiar behavior.