Life history parameters and diet of Risso's dolphins,Grampus griseus,from southeastern South Africa

The life history of Risso's dolphins (Grampus griseus) remains poorly known and data from strandings can help provide important information. Data from 126 Risso's dolphins stranded or bycaught along the southeastern coastline of South Africa between 1958 and 2017 were analyzed in relation to their sex, age structure, and diet. Mean estimated length at birth was 146.9 cm, while maximum length was 325 cm for males and 313 cm for females; small sample sizes precluded detailed examination of sexual dimorphism. Age estimates for 33 individuals (14 males, 17 females, 2 unknown sex) indicated a maximum age of 13 years (males) and 17 years (females), respectively; the oldest animal was 19 years (unknown sex). Mean length and age at attainment of sexual maturity were estimated at 280 cm and 7.1 years in males and at 282 cm and 7.7 years in females. Stomach contents from 27 individuals showed that diets of immature and mature males and females overlapped and consisted predominantly of cephalopods. Reported strandings decreased between 2000 and 2017, possibly due to a lack of reporting associated with a ban on driving on beaches or related to the collapse of the local “chokka” squid (Loligo reynaudii) fishery in 2014–2015.     

Noise does not equal bias in assessing the evolutionary history of the angiosperm flora of China: A response to Qian (2019)

In response to our paper on the evolutionary history of the Chinese flora, Qian suggests that certain features of the divergence time estimation employed might have led to biased conclusions in Lu et al (2018). Here, we consider Qian's specific criticisms, explore the extent of uncertainty in the data and demonstrate that (i) no systematic bias toward dates that are too young or too old is detected in Lu et al.; (ii) constraint of the crown age of angiosperms does not bias the generic ages estimated by Lu et al.; and (iii) ages derived from the Chinese regional phylogeny do not bias the conclusions reported by Lu et al. All these analyses confirm that the conclusions reported previously are robust. We argue that, like many large-scale biodiversity analyses, sources of noise in divergence time estimation are to be expected, but these should not be confused with bias.     

A simple topographical model to predict Golden Eagle Aquila chrysaetos space use during dispersal

Many large raptors exploit or rely on anabatic and orographic winds which provide vertical lift, to supplement or provide the energy fuelling flight. Airspace is therefore a critical habitat for such large raptors and its use is subject to the underlying terrestrial topography, because particular topographical features are more likely to provide wind-energetic lift. Accordingly, ridges and/or ‘rugged topography’ are common preferred features in habitat use by large raptors. Our study aimed to provide a simple model of space use for a large raptor, the Golden Eagle Aquila chrysaetos, based on thousands of GPS telemetry records during juvenile dispersal of 92 birds tagged as nestlings between 2007 and 2016 across upland Scotland. Model development was based on the hypothesis that four topographical variables would be influential: slope, aspect, altitude and distance from ridge. The telemetry dataset was divided into training and two testing components. The first testing set was derived by a temporal split resulting in approximately equal sample size on records and some temporal overlap in individuals’ records with training data. The second testing set involved no individuals from the training set. Aspect was removed early in training model development because it was not influential. The model found that young Golden Eagles preferred, or used according to availability, space above slopes greater than 10°, at an altitude of ≥ 300 m, and within 300 m of a ridge. The test data were highly correlated with those from the training data in the model variables, and performance as regard to expected preferences from the model was improved in both test datasets, indicating the model was robust. Given the apparent universal nature of large raptor dependence on topography, that topography is relatively immutable according to time and use, and that topographical data are readily available, we commend our approach to other habitat preference studies of Golden Eagles and other large raptors elsewhere.     

Specificity of extrafloral nectar induction by herbivores differs among native and invasive populations of tallow tree

Background and Aims

Invasive plants can be released from specialist herbivores and encounter novel generalists in their introduced ranges, leading to variation in defence among native and invasive populations. However, few studies have examined how constitutive and induced indirect defences change during plant invasion, especially during the juvenile stage.

Methods

Constitutive extrafloral nectar (EFN) production of native and invasive populations of juvenile tallow tree (Triadica sebifera) were compared, and leaf clipping, and damage by a native specialist (Noctuid) and two native generalist caterpillars (Noctuid and Limacodid) were used to examine inducible EFN production.

Key results

Plants from introduced populations had more leaves producing constitutive EFN than did native populations, but the content of soluble solids of EFN did not differ. Herbivores induced EFN production more than simulated herbivory. The specialist (Noctuid) induced more EFN than either generalist for native populations. The content of soluble solids in EFN was higher (2·1 times), with the specialist vs. the generalists causing the stronger response for native populations, but the specialist response was always comparable with the generalist responses for invasive populations.

Conclusions

These results suggest that constitutive and induced indirect defences are retained in juvenile plants of invasive populations even during plant establishment, perhaps due to generalist herbivory in the introduced range. However, responses specific to a specialist herbivore may be reduced in the introduced range where specialists are absent. This decreased defence may benefit specialist insects that are introduced for classical biological control of invasive plants.     

Some aspects of the biology of the hedgehog (Erinaceus europaeus L.) in the Manawatu,New Zealand

In a study area of 16.3 ha of dairy pasture and pine plantations in the Manawatu region of the southern North Island, 150 hedgehogs were marked and 356 recaptures recorded between 1 January 1970 and 24 June 1971. Population density was estimated at between 1.1/ha in winter and 2.5/ha in summer and autumn. Only 11 females and 5 males were considered to be residents, and these used overlapping feeding ranges of similar extent. Concentrations of food organisms became foci of hedgehog activity. During winter, when an estimated 20% of the population died, movement was restricted to the vicinity of the nest site; the hedgehogs hibernated fitfully during July‐October. The breeding season as such extended at least from November to March; some breeding activity was observed in most months, however. The average life span of adults was 1.97 years. The causes of 6 natural deaths and the incidence of abscesses and external parasites were noted.     

Juvenile hormone-like substances can induce vitellogenesis in the tick Ornithodoros moubata (Acarina: Argasidae)

Topical application of different juvenile hormone analogs (JHA) or of a mixture of stereoisomers of insect juvenile hormone (JH) 1 and 3 to fed virgin female Ornithodoros moubata immediately after feeding induced vitellogenesis and egg-laying in up to 70% of treated females. In controls only 13.7% oviposited. The eggs were sterile, with abnormal shape, but their number versus the weight of engorged females was normal or sometimes greater than in mated females. However, preoviposition period was longer than in mated females.

It was more difficult to induce egg-laying by similar topical applications 100 days after feeding of virgin females. A maximum of 58% of ovipositing females was obtained with a very high dosage of JH mixture (500 fig). Injection of this mixture into the females was more potent; 15 to 50 fig induced oviposition in about 60% of the females. The preoviposition period was also longer than in control females.

Our results suggest the presence of a JH-like substance which is involved in the hormonal control of vitellogenesis. However, since natural isomers of JH were much less efficient than isomeric mixtures or JHA, we suppose that the natural tick hormone does not correspond to JH, but rather to a JH-like substance.     

Protein production in components of the accessory gland complex of male Melanoplus sanguinipes (Insecta: Orthoptera)

Protein production during sexual maturation or after allatectomy (followed by juvenile hormone replacement therapy) has been examined in the long hyaline glands, short hyaline glands, white glands, and seminal vesicles, which make up the accessory gland complex of male Melanoplus sanguinipes. During maturation, the amount of protein in the long hyaline glands increases about 14-fold, and in each of the other components between 5- and 6-fold. Most protein accumulates between days 3 and 5, and this is reflected in high levels of incorporation of radiolabelled leucine in this period.

The components show differential sensitivity to the effects of allatectomy. After this operation, the protein content of, and incorporation of radiolabel into, the long hyaline glands remain near the day 0 level. In the white glands and short hyaline glands, allatectomy also has a marked, though less severe, effect on protein synthesis and accumulation. The seminal vesicles are least affected by allatectomy and continue to accumulate protein (though more slowly) to about 60% of the normal level by day 10. Juvenile hormone compounds applied topically to allatectomized insects on day 2 restored the ability of the gland components to accumulate proteins, though to differing degrees. JHI is the most effective compound, stimulating synthesis and accumulation of protein to near normal levels by day 10, whereas application of JHIII or Stauffer's synthetic JH led to only partial restoration of protein synthesis in the glands.     

Combined effect of cyprid age and lipid content on larval attachment and metamorphosis of Balanus amphitrite darwin

Various algal diets of different lipid content and composition were used to rear batches of naupliar larvae of Balanus amphitrite. The cyprids in these larval batches differed in lipid content and were used to investigate the combined effect of cyprid lipid content and cyprid age on attachment and metamorphosis. For this purpose, cyprids were aged for 0,3 and 6 d at 8°C prior to utilization in laboratory attachment assays. The percentage attachment of cyprids with similar lipid content differed significantly among the three age categories. A strong and a weak positive relationship between cyprid lipid content and attachment were monitored in young and old cyprids, respectively. A significant interaction (two‐way ANOVA) between cyprid age and lipid content was observed, indicating that these factors jointly affect larval attachment and metamorphosis in B. amphitrite from the beginning of the cyprid stage.     

Effect of cyprid age on the settlement of balanus amphitrite darwin in response to natural biofilms

Larval settlement of the barnacle Balanus amphitrite Darwin (Cirripedia, Balanidae) is influenced by natural biofilms. In previous work by others, discriminatory settlement of aged cyprids has been observed in response to biofilms of different age. This study extends prior work by considering the effect of the age of cyprids on the outcome of settlement assays. Settlement was investigated with 0‐day‐old (newly metamorphosed) and 5‐day‐old cyprids. Biofilms under investigation were developed in the field for periods of 5 d and 1 month, and were subsequently included in laboratory settlement assays with a choice between a filmed and an unfilmed substratum. The bioassay was modified from the conventional horizontal dish design in order to generate a low water surface‐to‐volume ratio, which served to suppress larval entrapment in an organic layer on the water surface. Irrespective of cyprid age, a clear discrimination between a filmed and an unfilmed substrata was observed, and the preference for filmed or unfilmed substratum was dependent on the age of the cyprids. Settlement of 0‐day‐old cyprids was inhibited by a biofilmed substratum whereas induction occurred with aged cyprids. This pattern of settlement was independent of biofilm age. Bacterial abundance on unfilmed substrata in treatments and controls was significantly lower than that on biofilmed surfaces, confirming that bacterial contamination did not change the qualitative option during the assay.