A multiyear survey of helminths from wild saddleback (Leontocebus weddelli) and emperor (Saguinus imperator) tamarins

The establishment of baseline data on parasites from wild primates is essential to understand how changes in habitat or climatic disturbances will impact parasite–host relationships. In nature, multiparasitic infections of primates usually fluctuate temporally and seasonally, implying that the acquisition of reliable data must occur over time. Individual parasite infection data from two wild populations of New World primates, the saddleback (Leontocebus weddelli) and emperor (Saguinus imperator) tamarin, were collected over 3 years to establish baseline levels of helminth prevalence and parasite species richness (PSR). Secondarily, we explored variation in parasite prevalence across age and sex classes, test nonrandom associations of parasite co‐occurrence, and assess the relationship between group size and PSR. From 288 fecal samples across 105 individuals (71 saddleback and 34 emperor tamarins), 10 parasite taxa were identified by light microscopy following centrifugation and ethyl‐acetate sedimentation. Of these taxa, none were host‐specific, Dicrocoeliidae and Cestoda prevalences differed between host species, Prosthenorchis and Strongylida were the most prevalent. Host age was positively associated with Prosthenorchis ova and filariform larva, but negatively with cestode and the Rhabditoidea ova. We detected no differences between expected and observed levels of co‐infection, nor between group size and parasite species richness over 30 group‐years. Logistic models of individual infection status did not identify a sex bias; however, age and species predicted the presence of four and three parasite taxa, respectively, with saddleback tamarins exhibiting higher PSR. Now that we have reliable baseline data for future monitoring of these populations, next steps involve the molecular characterization of these parasites, and exploration of linkages with health parameters.     

Composition and Proposed Nutritional Importance of Exudates Eaten by Saddleback (Saguinus fuscicollis) and Mustached (Saguinus mystax) Tamarins

I provide the first comprehensive data on the composition and mineral content of exudates eaten by saddleback (Saguinus fuscicollis) and mustached tamarins (S. mystax) and assess Garber's (1984; 1993) hypotheses on the potential nutritional importance of exudates in the diet of tamarins. In accordance with his initial findings, nutritional analyses show that the gums consumed are relatively high in calcium and may serve to balance a diet otherwise low in this mineral and high in phosphorus. However, the data on the seasonal variation in the amount consumed do not support the hypothesis that exudates are of particular nutritional importance during the later stages of gestation or lactation for saddleback or mustached tamarins.     

The range of the golden-mantle tamarin, <Emphasis Type="Italic">Saguinus tripartitus</Emphasis> (Milne Edwards, 1878): distributions and sympatry of four tamarin species in Colombia,Ecuador, and northern Peru

A detailed understanding of the range of the golden-mantle tamarin, Saguinus tripartitus (Milne Edwards, 1878), in Amazonian Peru and Ecuador is of particular relevance, not only because it is poorly known but also because it was on the basis of its supposed sympatry with the saddleback tamarin (S. fuscicollis lagonotus) that Thorington (Am J Primatol 15:367-371, 1988) argued that it is a distinct species rather than a saddleback tamarin subspecies, as was believed by Hershkovitz (Living new world monkeys, vol I. The University of Chicago Press, Chicago, 1977). A number of surveys have been carried out since 1988 in the supposed range of S. tripartitus, in both Ecuador and Peru. Here we summarize and discuss these issues and provide a new suggestion for the geographic range of this species; that is, between the ríos Napo and Curaray in Peru and extending east into Ecuador. We also review current evidence for the distributions of Spix's black-mantle tamarin (S. nigricollis nigricollis), Graells' black-mantle tamarin (S. n. graellsi), and the saddleback tamarin (S. fuscicollis lagonotus), which are also poorly known, and examine the evidence regarding sympatry between them. We conclude that despite the existence of a number of specimens with collecting localities that indicate overlap in their geographic ranges, the fact that the four tamarins are [corrected] of similar size and undoubtedly very similar in their feeding habits militates strongly against the occurrence of sympatry among them.     

Long-term patterns of sleeping site use in wild saddleback (Saguinus fuscicollis) and mustached tamarins (S. mystax): effects of foraging, thermoregulation, predation, and resource defense constraints

Sleeping sites are an important aspect of an animal's ecology given the length of time that they spend in them. The sleep ecology of wild saddleback and mustached tamarins is examined using a long-term data set covering three mixed-species troops and 1,300+ tamarin nights. Seasonal changes in photoperiod accounted for a significant amount of variation in sleeping site entry and exit times. Time of exit was more closely correlated with sunrise than time of entry was with sunset. Both species entered their sleeping sites when light levels were significantly higher than when they left them in the morning. Troops of both species used >80 individual sites, the majority being used once. Mustached tamarins never used the same site for more than two consecutive nights, but saddlebacks reused the same site for up to four consecutive nights. Mustached tamarins slept at significantly greater heights than saddleback tamarins. There were consistent interspecific differences in the types of sites used. Neither the presence of infants, season, nor rainfall affected the types or heights of sites chosen. Sleeping sites were located in the central area of exclusive use more often than expected, and their position with respect to fruiting trees indicated a strategy closer to that of a multiple central place forager than a central place forager. These findings are discussed in light of species ecology, with particular reference to predation risk, which is indicated as the major factor influencing the pattern of sleeping site use in these species.     

Erratum to: The range of the golden-mantle tamarin, <Emphasis Type="Italic">Saguinus tripartitus</Emphasis> (Milne-Edwards, 1878): distributions and sympatry of four tamarins in Colombia,Ecuador, and northern Peru

A detailed understanding of the range of the golden-mantle tamarin, Saguinus tripartitus (Milne Edwards, 1878), in Amazonian Peru and Ecuador is of particular relevance, not only because it is poorly known but also because it was on the basis of its supposed sympatry with the saddleback tamarin (S. fuscicollis lagonotus) that Thorington (Am J Primatol 15:367–371, 1988) argued that it is a distinct species rather than a saddleback tamarin subspecies, as was believed by Hershkovitz (Living new world monkeys, vol I. The University of Chicago Press, Chicago, 1977). A number of surveys have been carried out since 1988 in the supposed range of S. tripartitus, in both Ecuador and Peru. Here we summarize and discuss these issues and provide a new suggestion for the geographic range of this species; that is, between the ríos Napo and Curaray in Peru and extending east into Ecuador. We also review current evidence for the distributions of Spix’s black-mantle tamarin (S. nigricollis nigricollis), Graells’ black-mantle tamarin (S. n. graellsi), and the saddleback tamarin (S. fuscicollis lagonotus), which are also poorly known, and examine the evidence regarding sympatry between them. We conclude that despite the existence of a number of specimens with collecting localities that indicate overlap in their geographic ranges, the fact that the four tamarin species are of similar size and undoubtedly very similar in their feeding habits militates strongly against the occurrence of sympatry among them.     

Saddleback Deformities in Fish Species Collected from the Arabian Gulf Coast of Jubail City,Saudi Arabia

The saddleback syndromes were observed in several commercial fishes obtained from Saudi Arabian coast of the Arabian Gulf. These deformities resulting in missing dorsal spines or rays, sometimes accompanied by a depression in the dorsal profile, were found in ten fish species from seven families. Other morphological abnormalities such as scale disturbances, lateral line deformity, and kyphosis, the presence of a lesion, slight ambicoloration, and supraneural deformities accompanying the saddleback deformity were also observed. The occurrence of similar deformities across such a spectrum of fishes from the same location suggests that the abnormalities were induced by something in the environment common to all these species.     

Distance sampling techniques compared for a New Zealand endemic passerine (

The effectiveness of line- and point-transect distance sampling methods was compared for estimating the density of a conspicuous endemic passerine, the North Island saddleback Philesturnus carunculatus rufusater, in two forest habitats on Tiritiri Matangi Island, Hauraki Gulf, New Zealand. The reference population abundance in each habitat was calculated through an intensive capture, colour-banding, and resighting effort. Line transects consistently produced unbiased estimates of density for both sites at two time periods (morning and afternoon), and proved to be the most efficient of the distance sampling methods tested. Point-transect methods proved to be biased in this instance, consistently producing overestimates of density for this species, and were unreliable as indices of the small differences in density between habitats. Transect counts conducted from established walking tracks underestimated both density and the variance of estimated density. We conclude that in situations requiring estimates of absolute density for North Island saddleback, a series of randomly positioned line transects will accurately represent the density of individuals. Furthermore, this study highlights the need to pilot distance survey techniques on the species of interest to detect possible violation of the assumptions underlying these methods. We question the widespread use of point-transect counts for censusing avian species without such preliminary investigation, and recommend further comparisons of distance sampling methods in New Zealand with reference populations where opportunity provides.     

Developing population models for guiding reintroductions of extirpated bird species back to the New Zealand mainland

Population models are useful tools to guide management as they allow us to project growth and persistence of wildlife populations under different scenarios. Nevertheless, good data are needed to produce reliable models, and this requirement is problematic in some situations. North Island saddlebacks (Philesturnus rufusater) were reintroduced to Boundary Stream Mainland Island in September 2004, and this was the first time this species had occurred in an unfenced mainland area since their extirpation in the 19th century. This situation creates a challenging scenario for population modelling, as this species has never been studied in the presence of mainland predators, and management of these predators will be the key factor determining whether the population survives. In this paper we present an approach for developing a “prior model” before a reintroduction takes place. We use data from the reintroduced saddleback population on Mokoia Island to develop a model of how saddleback populations are regulated in the absence of mammalian predators. We use this model to project growth of a reintroduced population when vital rates are reduced by predation and also to project responses of source populations to harvesting of birds for translocation. We then incorporate data from the reintroduced North Island robin (Petroica longipes) population at Paengaroa Mainland Island to model the relationship between population parameters and predator tracking rates. The combined model can be used to predict the level of predator control needed to ensure growth of the saddleback population, but the prediction is contingent on guessing the relative vulnerability of robins and saddlebacks to predation. We envision using a Bayesian approach to update such prior models as site-specific data become available after reintroduction.     

Mutual Wattle Ornaments in the South Island Saddleback (Philesturnus carunculatus) Function as Armaments

Many birds have ornamental traits that are expressed in both sexes. Wattles—colorful fleshy structures that hang from the lower bill—are frequent among birds, but remain poorly understood and are generally presumed to be under sexual selection. The South Island saddleback (Philesturnus carunculatus) is an endangered bird endemic to New Zealand in which both males and females possess wattles. We used behavioral observations, morphological measures, and a playback experiment to investigate the role of wattles in saddlebacks during territorial encounters. Wattles were monomorphic when controlled for body mass, and became engorged with blood in both sexes during visual displays. In a playback experiment using male song, wattle engorgement was significantly associated with territorial intrusions in males but not in females. However, female wattle engorgement was significantly more likely during playback experiments in the absence of their mate, suggesting wattles are used in territorial defense by both sexes. The markedly similar use of wattles by both males and females in visual displays as a response to territorial intrusions supports the hypothesis that these elaborate structures function in part as armaments.     

The gut microbiome and metabolome of saddleback tamarins (Leontocebus weddelli): Insights into the foraging ecology of a small‐bodied primate

Body mass is a strong predictor of diet and nutritional requirements across a wide range of mammalian taxa. In the case of small‐bodied primates, because of their limited gut volume, rapid food passage rate, and high metabolic rate, they are hypothesized to maintain high digestive efficiency by exploiting foods rich in protein, fats, and readily available energy. However, our understanding of the dietary requirements of wild primates is limited because little is known concerning the contributions of their gut microbiome to the breakdown and assimilation of macronutrients and energy. To study how the gut microbiome contributes to the feeding ecology of a small‐bodied primate, we analyzed the fecal microbiome composition and metabolome of 22 wild saddleback tamarins (adult body mass 360–390 g) in Northern Bolivia. Samples were analyzed using high‐throughput Illumina sequencing of the 16 S rRNA gene V3‐V5 regions, coupled with GC‐MS metabolomic profiling. Our analysis revealed that the distal microbiome of Leontocebus weddelli is largely dominated by two main bacterial genera: Xylanibacter and Hallella (34.7 ± 14.7 and 22.6 ± 12.4%, respectively). A predictive analysis of functions likely carried out by bacteria in the tamarin gut demonstrated the dominance of membrane transport systems and carbohydrate metabolism as the predominant metabolic pathways. Moreover, given a fecal metabolome composed mainly of glucose, fructose, and lactic acid (21.7 ± 15.9%, 16.5 ± 10.7%, and 6.8 ± 5.5%, respectively), the processing of highly fermentable carbohydrates appears to play a central role in the nutritional ecology of these small‐bodied primates. Finally, the results also show a potential influence of environmentally‐derived bacteria in colonizing the tamarin gut. These results indicate high energetic turnover in the distal gut of Weddell's saddleback tamarin, likely influenced by dominant bacterial taxa that facilitate dietary dependence on highly digestible carbohydrates present in nectar, plant exudates, and ripe fruits.     

Factors Affecting Group Spread within Wild Mixed-Species Troops of Saddleback and Mustached Tamarins

We examined group spread and interindividual spacing within wild mixed-species troops of saddleback (Saguinus fuscicollis) and mustached (Saguinus mystax) tamarins. Mustached tamarin groups were spread over larger areas than those of saddleback tamarins. Group size and behavior affected group spread and interspecific proximity: larger groups of both species were dispersed over greater areas, and the larger troop had the lowest degree of interspecific proximity. Behavior also affected group spread and interspecific proximity: when traveling individuals were spread over a larger area, and the distance between heterospecifics was greater than when stationary. We examined spatial proximity using data on the distance from nearest neighbor. Overall, distance to nearest neighbor was not affected by group size. Based on specific behaviors, foraging saddleback tamarins were significantly nearer conspecifics than to mustached tamarins. Tamarins have polymorphic color vision, and trichromats—having 3 types of visual pigment—versus dichromatic individuals—with two types of pigment—may be better at perceiving yellow or russet colored predators and conspecifics than their dichromatic counterparts are. Color vision status affected spatial positioning, with vigilant trichromats being further from their neighbors than their dichromatic conspecifics were. We discuss the findings with respect to the ecology of the species. Specifically, interspecific differences in group spread and spatial proximity are related to differences in the supports used, and the effect of troop size on interspecific proximity is related to increased resource competition. The finding that trichromats are further from their neighbors represents the first example of a behavioral correlate of color vision ability in a wild species with polymorphic color vision, and is explained through the perception of predation risk.     

Multi-scale habitat models for reintroduced bird populations: a case study of South Island saddlebacks on Motuara Island

Understanding resource selection by animals is important when considering habitat suitability at proposed release sites within threatened species recovery programmes. Multi-scale investigatory approaches are increasingly encouraged, as the patchy distribution of suitable habitats in fragmented landscapes often determines species presence and survival. Habitat models applied to a threatened New Zealand forest passerine, the South Island saddleback (Philesturnus carunculatus carunculatus), reintroduced to Ulva Island (Stewart Island) found that at landscape scale breeding pairs? preferences for sites near the coast were driven by micro-scale vegetation structure. We tested these results by examining models of breeding site selection by a reintroduced saddleback population on Motuara Island (Marlborough Sounds) at two scales: (1) micro-scale, for habitat characteristics that may drive breeding site selection, and (2) landscape scale, for variations in micro-scale habitat characteristics that may influence site colonisation in breeding pairs. Results indicated that birds on Motuara Island responded similarly to those on Ulva Island, i.e. birds primarily settled at the margins of coastal scrub and forest and later cohorts moved into larger stands of coastal forest where they established breeding territories. Plant species composition was also important in providing breeding saddleback pairs with adequate food supply and nesting support. However, Motuara Island birds differed in their partitioning of habitat use: preferred habitats were used for nesting while birds were foraging outside territorial boundaries or in shared sites. These differences may be explained because Motuara has a more homogeneous distribution of microscale habitats throughout the landscape and a highly bird-populated environment. These results show that resource distribution and abundance across the landscape needs to be accounted for in the modelling of density?bird?habitat relationships. In the search for future release sites, food (invertebrates and fruiting tree species) should be abundant close to available nesting sites, or evenly spread and available throughout the landscape.     

Leaders of progressions in wild mixed-species troops of saddleback (Saguinus fuscicollis) and mustached tamarins (S. mystax), with emphasis on color vision and sex

Leadership of travel progression is an important aspect of group living. It is widely believed that trichromacy evolved to facilitate the detection and selection of fruit in the dappled light of a forest. Further, it has been proposed that in New World primate species, which typically contain a range of color vision phenotypes, at least one female in a group will be trichromatic (i.e., having three types of visual pigment, in contrast to the two types of pigment found in dichromatic individuals) and will lead the group to fruiting trees. We examine progression leadership within two wild mixed-species troops of saddleback (Saguinus fuscicollis) and mustached (Saguinus mystax) tamarins over a complete year. As whole units, the mixed-species troops were most frequently led by a mustached tamarin. This is the first time that mixed-species group leadership and individual leadership have been quantified in these tamarin species. In terms of single-species intragroup leadership, neither the visual status (dichromatic or trichromatic) nor the sex of individuals had a consistent effect across species. Saddleback tamarin groups were led by males more frequently than females, while evidence suggests that mustached tamarins may be female-led. The notion that all groups contain at least one trichromatic female that leads the troop to feeding trees was not supported.     

Winter predation of diapausing cocoons of slug caterpillars (Lepidoptera: Limacodidae)

Predators exert strong top-down pressure on herbivorous insects, but research on how predators affect herbivore fitness often focuses on the more active juvenile and adult life stages while ignoring the pupal or cocoon life stage. Few studies have investigated predation of lepidopteran pupae or cocoons and even fewer have investigated species that are not forest pests. Here we present a study on overwinter survival for two moth species in the family Limacodidae, a group of polyphagous species found in deciduous forests. We placed cocoons of the saddleback caterpillar, Acharia stimulea (Clemens), and the spiny oak-slug caterpillar, Euclea delphinii (Boisduval), in the field under saplings of six different tree species and monitored predation and survival. This is the first study to examine predation rate among different host plants within a site. We found that cocoon predation was fairly high and differed significantly between limacodid species (29% for A. stimulea vs. 22% for E. delphinii). Predation rate did not differ among the six host plant species that we tested and also did not vary annually. Through phenotypic selection analyses, we found that cocoon mass affected both the likelihood of predation and overwinter survival; larger cocoons were less likely to be depredated and more likely to successfully emerge the following year. Overall our results indicate that cocoon predation is an important source of mortality for these two limacodid species and that there may be positive selection for greater cocoon mass for both limacodid species.     

Effect of saddleback syndrome and vertebral deformity on the body shape and size in hatchery-reared juvenile red spotted grouper, Epinephelus akaara (Perciformes: Serranidae): a geometric morphometric approach

This study examined how saddleback syndrome (SBS) and vertebral deformity affect the body shape and size of juvenile stage red spotted grouper, Epinephelus akaara, using the landmark‐based geometric morphometrics method. According to the criterion of skeletal conditions, three groups, i.e. vertebral deformity, SBS, and normal groups, were identified. The results revealed significant differences in body shape among the three groups, in which the vertebral‐deformed group had the deepest mid‐body, the broadest anterior part, and a shortened caudal peduncle, while the SBS group showed the shallowest mid‐body and the narrowest anterior part. The normal group had a body shape intermediate between the vertebral and SBS groups. A comparison of body size among the three groups revealed significant differences in centroid size, with the vertebral‐deformed and SBS groups showing smallest and largest centroid size, respectively. This study illuminates that not all skeletal deformities lead to smaller body size. We suggest that rearing conditions might have caused the deformities reported herein.     

Vigilance in Single- and Mixed-Species Groups of Tamarins (Saguinus labiatus and Saguinus fuscicollis)

By forming larger sizes of groups, individuals benefit from a decrease in vigilance, but the collective vigilance of the group as a whole is not compromised. We examined whether this group size effect is apparent in mixed-species groups of red-bellied tamarins (S. labiatus) and saddleback tamarins (S. fuscicollis) which form stable and permanent associations in the wild. We studied general vigilance and responses to hidden threatening stimuli in five captive groups of each species, while they were housed in single- and mixed-species groups. For vigilance, the individual rate was lower in the larger mixed-species groups than in the smaller single-species groups. In addition, the amount of time when at least one individual was vigilant was higher in mixed-species groups. This suggests that the tamarins alter their vigilance behavior in the presence of the other species. In response to hidden threats, both species performed brief vigilance checks and frequencies of checking did not differ in single- and mixed-species groups. However, both species had a significant reduction in the mean duration per check, and there was a reduced total amount of time spent vigilance checking in the mixed-species groups compared to the single-species groups, demonstrating the group size effect. Overall the mixed-species groups had a higher number and mean duration of checking than the smaller single-species groups. Given that the two species share a common set of predators, and respond to each other's alarm calls, these findings provide strong evidence that individuals of both tamarin species may be able to benefit from forming mixed-species groups via improved vigilance and monitoring of threats.     

The Equivocal Relationship Between Territoriality and Scent Marking in Wild Saddleback Tamarins (<Emphasis Type="Italic">Saguinus fuscicollis</Emphasis>)

Researchers have often assumed that scent marking serves a territorial function in callitrichines, although some controversy exists. To fulfill such a function, scent marks should 1) prevent intrusions, 2) ensure access to feeding resources, 3) enable avoidance of intergroup encounters, or 4) play an important role in the aggressive encounters between groups. We studied 13 saddleback tamarins (Saguinus fuscicollis) belonging to 3 free-ranging groups, which formed mixed-species troops with moustached tamarins (S. mystax) in the Amazonian rain forest of Peru. None of the predictions were confirmed. The tamarins used a border-marking strategy, marking more on the periphery of their territory. However, feeding trees in overlap and encounter areas received more scent marking but were still visited by neighboring groups. Intergroup encounters occurred more often than expected, and scent-marking frequency was not higher during them than when no other group was present. It appears that instead of defending a territory in the classic sense, the tamarins are optimizing signal transmission by depositing their scents where the probability of detection by neighbors is higher. Saddleback tamarins may use shared areas of their home ranges to exchange information with neighboring groups, perhaps regarding reproductive opportunities.     

A New Subspecies of <Emphasis Type="Italic">Saguinus fuscicollis</Emphasis> (Primates,Callitrichidae)

Saddleback tamarins (Saguinus fuscicollis, S. melanoleucus, and S. tripartitus) occur in the upper Amazon, west of the rios Madeira and Mamoré–Guaporé to the Andes. They currently comprise 13 species and subspecies in Bolivia, Brazil, Colombia, Ecuador, and Peru. Here we report on a previously undescribed subspecies of Saguinus fuscicollis from the interfluvium of the lower rios Madeira and Purus in the central Amazon of Brazil. It is a distinct form with a very pronounced mottling on the back giving the appearance of a saddle, a characteristic shared by the 3 species, and the reason for their collective common name. The lack of a white superciliary chevron and its highly mottled ochraceous-dark brown to black saddle that extends from the scapular region to the base of the tail distinguish the new taxon from Saguinus fuscicollis weddelli. The latter characteristic also distinguishes it from another saddleback tamarin (Saguinus fuscicollis ssp.) that has been reported immediately to the south of its range in the same interfluvium. We compare pelage coloration, external characters and craniometric measurements with its geographically closest relatives, Saguinus fuscicollis weddelli and S. f. avilapiresi, and indicate its probable geographic distribution in a small area between the rios Madeira and Purus, just south of the Rio Amazonas.     

Characterization of MHC class II B polymorphism in bottlenecked New Zealand saddlebacks reveals low levels of genetic diversity

The major histocompatibility complex (MHC) is integral to the vertebrate adaptive immune system. Characterizing diversity at functional MHC genes is invaluable for elucidating patterns of adaptive variation in wild populations, and is particularly interesting in species of conservation concern, which may suffer from reduced genetic diversity and compromised disease resilience. Here, we use next generation sequencing to investigate MHC class II B (MHCIIB) diversity in two sister taxa of New Zealand birds: South Island saddleback (SIS), Philesturnus carunculatus, and North Island saddleback (NIS), Philesturnus rufusater. These two species represent a passerine family outside the more extensively studied Passerida infraorder, and both have experienced historic bottlenecks. We examined exon 2 sequence data from populations that represent the majority of genetic diversity remaining in each species. A high level of locus co-amplification was detected, with from 1 to 4 and 3 to 12 putative alleles per individual for South and North Island birds, respectively. We found strong evidence for historic balancing selection in peptide-binding regions of putative alleles, and we identified a cluster combining non-classical loci and pseudogene sequences from both species, although no sequences were shared between the species. Fewer total alleles and fewer alleles per bird in SIS may be a consequence of their more severe bottleneck history; however, overall nucleotide diversity was similar between the species. Our characterization of MHCIIB diversity in two closely related species of New Zealand saddlebacks provides an important step in understanding the mechanisms shaping MHC diversity in wild, bottlenecked populations.     

Tamarins: Alpha female,queen bee or white rat?

The saddleback tamarin (Saguinus fuscicollis)combines a number of behavioral and physiological attributes which seem to violate “rules” of ethology. Of particular interest is the combination of facultative polyandry and high paternal investment. The social organization and breeding system of the tamarin also appear to combine reproductive restraint with an extremely high reproductive potential. These paradoxes may be resolved by noting that the combination of ecological circumstances and breeding systems has produced a species of limited genetic variability. Inclusive fitness is an important factor in situations of low genetic variability and may explain these apparent paradoxes.